Thyroid Cancer
Thyroid cancer is a malignant neoplasm arising from the follicular or parafollicular (C) cells of the thyroid gland, most commonly presenting as a painless thyroid nodule with papillary carcinoma being the most prevalent histologic subtype.
Thyroid Cancer
Thyroid cancer is a malignant neoplasm arising from cells of the thyroid gland. The vast majority originate from thyroid follicular epithelial cells (papillary, follicular, anaplastic), while a smaller proportion arise from parafollicular C cells (medullary thyroid carcinoma). "Thyro-" comes from the Greek thyreos (shield) — the gland is shaped like a shield sitting across the anterior neck.
The clinical significance lies in the fact that thyroid cancer is one of the most curable solid organ malignancies when well-differentiated, yet carries a dismal prognosis when undifferentiated (anaplastic). Understanding the histological type is therefore the single most important determinant of behaviour and management [1][2].
2. Epidemiology
- Thyroid cancer accounts for ~2.6% of all cancers in Hong Kong but is associated with very low mortality (~0.4% of all cancer deaths) [1].
- There is an increasing trend worldwide, likely driven by increased detection via ultrasonography (incidentalomas) and true increases in papillary thyroid microcarcinomas [1].
- In HK, thyroid cancer is the 5th most common cancer in females and the 17th most common cancer in males [1].
| Feature | Detail |
|---|---|
| Sex ratio | M:F ≈ 1:3–4 (female predominance across all differentiated types) [1][2] |
| Age of presentation | 40–50s overall; papillary peaks at 30–50y; follicular peaks at 40–60y [1][2] |
| Prognosis by sex | Male gender is associated with a worse prognosis despite lower incidence [2] |
Why is thyroid cancer more common in females? Oestrogen receptors (ERα/ERβ) are expressed on thyroid follicular cells, and oestrogen promotes thyroid cell proliferation via MAPK and PI3K/AKT pathways. This hormonal sensitivity explains the F > M ratio and the peak around reproductive years.
| Type | % of all thyroid CA | Peak Age | M:F |
|---|---|---|---|
| Papillary | 80–90% | 30–50y | 1:2.5 |
| Follicular | 10–20% | 40–60y | 1:3 |
| Medullary (MTC) | ~5–7% | > 50y (sporadic), 20–30y (familial) | 1:1 |
| Anaplastic | ~3–5% | 60–70y | 1:1.5 |
| Lymphoma | ~1–5% | > 50y | 1:2 |
| Others (SCC, sarcoma, mets) | < 1% | Variable | Variable |
High Yield Exam Point
The two most testable facts about thyroid cancer epidemiology: (1) papillary carcinoma accounts for ~80–90% of all thyroid cancers, and (2) overall thyroid cancer has an excellent prognosis (except anaplastic — median survival < 6 months).
3. Anatomy and Function of the Thyroid Gland
Understanding the anatomy is critical because surgical anatomy dictates operative complications (recurrent laryngeal nerve injury, hypoparathyroidism) and lymphatic drainage dictates patterns of metastasis.
- Location: Anterior neck, wrapped around the trachea at the level of C5–T1 vertebrae, deep to the strap muscles (sternohyoid, sternothyroid).
- Structure: Two lateral lobes connected by an isthmus (overlying the 2nd–3rd tracheal rings). A pyramidal lobe (remnant of the thyroglossal duct) extends superiorly from the isthmus in ~50% of people.
- Weight: ~15–25 g in adults.
- Capsule: A thin true capsule surrounded by a false capsule (pretracheal fascia). This fascial layer is what surgeons dissect in to identify the recurrent laryngeal nerve (RLN) and parathyroids.
- Arterial: Superior thyroid artery (first branch of external carotid artery) and inferior thyroid artery (from thyrocervical trunk of subclavian artery). Occasionally a thyroidea ima artery arises directly from the aortic arch or brachiocephalic trunk.
- Venous: Superior and middle thyroid veins → internal jugular vein; inferior thyroid veins → brachiocephalic veins.
- The thyroid is one of the most vascular organs per gram of tissue — this is why a thyroid bruit can be heard in Graves' disease and why thyroid surgery requires meticulous haemostasis.
Lymphatic drainage follows a predictable pattern — this is essential for understanding metastatic spread:
| Level | Name | Significance |
|---|---|---|
| Level VI | Central compartment (pretracheal, paratracheal, prelaryngeal [Delphian]) | First echelon drainage for thyroid cancer; most commonly involved in papillary CA [1][3] |
| Level III, IV | Mid and lower jugular chain | Lateral cervical metastases |
| Level VII | Superior mediastinal | Retrosternal extension |
Why does papillary carcinoma spread to lymph nodes first? Papillary CA has a strong lymphatic predilection. In contrast, follicular CA preferentially invades blood vessels (haematogenous spread) — this is because follicular CA lacks papillary architecture and instead forms encapsulated masses that erode into capsular and vascular spaces.
| Structure | Relation | Surgical Significance |
|---|---|---|
| Recurrent laryngeal nerve (RLN) | Runs in the tracheo-oesophageal groove, passes deep to the inferior thyroid artery (variable) | Injury → hoarseness / vocal cord paralysis; bilateral injury → airway obstruction |
| External branch of superior laryngeal nerve (EBSLN) | Runs along the superior thyroid artery near the superior pole | Injury → loss of high-pitched voice (the "Amelita Galli-Curci nerve") |
| Parathyroid glands | Superior pair: posterior to upper pole; Inferior pair: posterior to lower pole (variable) | Inadvertent removal → hypocalcaemia |
| Trachea and oesophagus | Directly posterior to the isthmus and lobes | Direct tumour invasion → dyspnoea, stridor, dysphagia |
| Cell Type | Origin | Hormone | Cancer |
|---|---|---|---|
| Follicular epithelial cells | Endoderm (foramen cecum of tongue, descends via thyroglossal duct) | T3, T4 (thyroid hormones) | Papillary, follicular, anaplastic |
| Parafollicular C cells | Neural crest (ultimobranchial body) | Calcitonin | Medullary thyroid carcinoma |
Why does MTC produce calcitonin? Because MTC arises from parafollicular C cells whose normal physiological function is to secrete calcitonin (a peptide hormone that lowers serum calcium by inhibiting osteoclastic bone resorption). This is why calcitonin serves as a tumour marker for MTC [1][3].
- The hypothalamic-pituitary-thyroid (HPT) axis: TRH → TSH → T4/T3 production.
- Differentiated thyroid carcinoma (DTC) expresses TSH receptors [2]. This is clinically exploitable:
- TSH suppression with levothyroxine (T4) post-operatively reduces tumour stimulation.
- TSH stimulation (via recombinant human TSH or thyroid hormone withdrawal) enhances radioiodine (¹³¹I) uptake by residual tumour.
- Increased TSH is associated with increased thyroid cancer risk in patients with thyroid nodules [2].
4. Risk Factors and Etiology
| Risk Factor | Mechanism / Notes |
|---|---|
| Female gender | Oestrogen-mediated thyroid cell proliferation [2][3] |
| Family history of thyroid cancer (1st-degree relative) | ~10× increased risk for papillary CA if FHx positive [1][2] |
| Head and neck irradiation | Ionising radiation causes DNA double-strand breaks → oncogenic mutations (esp. RET/PTC rearrangements) → papillary CA. Strongest risk factor for PTC. Examples: brain irradiation for childhood leukaemia, TBI for bone marrow transplant, environmental radiation (e.g. Chernobyl, Fukushima) [2][3] |
| Familial syndromes | Gardner syndrome / FAP → papillary CA; MEN2A/2B → medullary CA; Cowden syndrome, Werner syndrome [1][2] |
| Hashimoto's thyroiditis | 60× risk of thyroid lymphoma (chronic antigen stimulation → lymphoid proliferation → MALT lymphoma → DLBCL) [1] |
| Iodine deficiency | Associated with follicular CA (chronic TSH stimulation drives follicular cell proliferation) [3] |
| Long-standing multinodular goitre (MNG) | Risk of de-differentiation → anaplastic carcinoma; also risk of lymphoma [1][3] |
| Previous differentiated thyroid CA | ~30% of anaplastic CA arise from de-differentiation of pre-existing papillary or follicular CA [1] |
Common Exam Mistake
Follicular adenoma is NOT a risk factor for follicular carcinoma [3]. These are distinct entities. Follicular adenoma is benign and does not "transform" into follicular CA. They share cytological features (which is why FNAC cannot distinguish them — you need histological demonstration of capsular/vascular invasion).
4.2 Familial Syndromes in Detail
| Type | Gene | Components | Thyroid Relevance |
|---|---|---|---|
| MEN1 | MEN1 (encodes menin, chr 11q13) | Parathyroid hyperplasia, Pancreatic endocrine tumours, Pituitary tumours (3 P's) | No direct thyroid cancer link |
| MEN2A | RET proto-oncogene (chr 10q11.2) | Medullary thyroid carcinoma + Phaeochromocytoma + Parathyroid hyperplasia | Nearly 100% develop MTC; prophylactic total thyroidectomy indicated [2][3] |
| MEN2B | RET proto-oncogene | Medullary thyroid carcinoma + Phaeochromocytoma + Mucosal neuromas / intestinal ganglioneuromatosis | Most aggressive MEN2 variant; MTC develops early (childhood) |
Prophylactic total thyroidectomy is indicated for all MEN2 patients since virtually all develop clinically apparent MTC [2]. Timing depends on the specific RET mutation codon risk category (ATA classification): highest-risk mutations (e.g. M918T in MEN2B) → thyroidectomy within the first 6 months of life; high-risk (e.g. C634R in MEN2A) → by age 5 years [4].
| Syndrome | Gene | Associated Thyroid CA |
|---|---|---|
| Familial adenomatous polyposis (FAP) / Gardner syndrome | APC | Papillary thyroid carcinoma (cribriform-morular variant) [1][2] |
| Cowden syndrome | PTEN | Follicular thyroid carcinoma, follicular adenoma |
| Werner syndrome | WRN | Various thyroid cancers |
| Carney complex | PRKAR1A | Follicular adenoma/carcinoma |
| Familial non-medullary thyroid cancer (FNMTC) | Multiple loci | Papillary CA (accounts for ~5% of PTC) |
- Hong Kong is an iodine-sufficient region (due to iodised salt and seafood-rich diet), so iodine deficiency-related follicular CA is relatively uncommon compared to iodine-deficient regions.
- NPC (nasopharyngeal carcinoma) is endemic in southern China/HK, and patients who receive head and neck radiotherapy for NPC are at increased risk of subsequent thyroid cancer (radiation-induced) — always ask about H&N cancer history, especially NPC [1].
- Thyroid cancer incidence in HK has been rising, partly attributed to increased ultrasonographic detection of incidental thyroid nodules (detection bias).
5. Pathophysiology and Pathogenesis
The mitogen-activated protein kinase (MAPK) pathway is critical to the development and progression of thyroid carcinoma [2].
Growth factor / RET → RAS → RAF (BRAF) → MEK → ERK → Cell proliferation5.1.1 Key Oncogenic Drivers by Type
| Mutation/Rearrangement | Thyroid Cancer Type | Notes |
|---|---|---|
| BRAF V600E | Papillary CA (~45%) | Most common mutation in PTC; associated with aggressive behaviour, extrathyroidal extension, lymph node metastasis, radioiodine refractance, and tall cell variant |
| RET/PTC rearrangements | Papillary CA (~20%) | Particularly common in radiation-induced PTC; common in children/young adults |
| RAS mutations (NRAS, HRAS, KRAS) | Follicular CA (~40%), follicular variant PTC | Also found in follicular adenoma → supports a "follicular pathway" of carcinogenesis |
| PAX8-PPARγ fusion | Follicular CA (~30%) | Transcription factor fusion → disrupts normal follicular differentiation |
| RET point mutations | Medullary CA (germline in familial, somatic in sporadic) | Gain-of-function mutations in RET tyrosine kinase receptor → constitutive activation |
| TP53 mutations | Anaplastic CA (~70%) | Loss of tumour suppressor → de-differentiation; often also BRAF or RAS mutant |
| TERT promoter mutations | Aggressive PTC, FTC, anaplastic | Associated with worse prognosis, tumour de-differentiation |
Why can anaplastic carcinoma arise from differentiated thyroid cancer? The "de-differentiation" model proposes that accumulation of additional mutations (especially TP53 and TERT promoter) in a pre-existing differentiated cancer causes loss of thyroid-specific gene expression (e.g. NIS, thyroglobulin, TSH receptor) → the tumour becomes undifferentiated, highly proliferative, and no longer responsive to radioiodine or TSH suppression [1][3].
- Differentiated thyroid carcinoma expresses TSH receptors [2].
- TSH binding activates cAMP signalling → promotes thyroid cell growth and iodine uptake.
- Clinical implications:
- Normal thyroid follicular cells express the sodium-iodide symporter (NIS) on their basolateral membrane → actively transports iodide into the cell.
- Well-differentiated thyroid cancers retain NIS expression (albeit often reduced) → this is the basis for radioiodine (¹³¹I) therapy and diagnostic whole-body scanning.
- Poorly differentiated and anaplastic cancers lose NIS expression → no radioiodine uptake → not amenable to ¹³¹I therapy.
Key Concept
The utility of radioiodine hinges on NIS expression. As thyroid cancers de-differentiate, they lose NIS expression, making them "radioiodine refractory." This is a critical threshold in management — when tumours no longer take up iodine, targeted therapies (e.g. lenvatinib, sorafenib) become the next line.
6. Classification
| Category | Subtypes | Cell of Origin |
|---|---|---|
| Well-differentiated thyroid carcinoma (WDTC) | Papillary thyroid carcinoma (PTC) — classical, follicular variant, tall cell, diffuse sclerosing, cribriform-morular, hobnail, etc. | Follicular epithelial cells |
| Follicular thyroid carcinoma (FTC) — minimally invasive, encapsulated angioinvasive, widely invasive; Hürthle (oncocytic) cell carcinoma | Follicular epithelial cells | |
| Poorly differentiated thyroid carcinoma (PDTC) | Insular carcinoma and others meeting Turin criteria | Follicular epithelial cells |
| Undifferentiated (anaplastic) thyroid carcinoma | — | Follicular epithelial cells (de-differentiated) |
| Medullary thyroid carcinoma (MTC) | Sporadic, familial (MEN2A, MEN2B, FMTC) | Parafollicular C cells |
| Other | Thyroid lymphoma, SCC, sarcoma, metastatic disease | Various |
6.1.1 Papillary Thyroid Carcinoma — Variant Overview
| Variant | Key Feature | Prognosis |
|---|---|---|
| Classical PTC | Papillary architecture, psammoma bodies, Orphan Annie nuclei | Excellent |
| Follicular variant | Follicular architecture but nuclear features of PTC | Excellent (encapsulated) to moderate (infiltrative) |
| Tall cell variant | Cells 3× taller than wide; associated with BRAF V600E; more aggressive | Poorer than classical PTC [1][2] |
| Diffuse sclerosing variant | Dense sclerosis, psammoma bodies, lymphocytic infiltration; young patients | Moderate |
| Cribriform-morular variant | Associated with FAP/Gardner syndrome | Good |
| Hobnail variant | Apical nuclei protruding like hobnails | Poor (aggressive) |
| Columnar cell variant | Tall columnar cells, supranucluar/infranuclear vacuoles | Poor |
Staging in thyroid cancer is unique because age is incorporated as a staging criterion for differentiated thyroid cancer (DTC):
- Age < 55 years: maximum Stage II (even with distant metastases) — reflects excellent prognosis.
- Age ≥ 55 years: staged I–IVB based on T, N, M.
- Anaplastic carcinoma: automatically Stage IV regardless of extent (IVA = intrathyroidal, IVB = extrathyroidal extension, IVC = distant mets).
Why Does Age Matter So Much?
Young patients with DTC have remarkable survival even with nodal and distant metastases (5-year survival > 95%). The biology in young patients is fundamentally different — tumours are more differentiated, more radioiodine-avid, and less likely to harbour aggressive mutations like TERT promoter mutations.
For recurrence risk in DTC post-surgery, the ATA uses a three-tier system:
| Risk | Criteria | Recurrence Rate |
|---|---|---|
| Low | Intrathyroidal DTC, ≤5 pathological N1 micrometastases ( < 0.2 cm), no vascular invasion, no aggressive histology, no RAI uptake outside thyroid bed, no BRAF V600E (if PTC) | 1–3% |
| Intermediate | Minor extrathyroidal extension, > 5 N1 nodes or any N1 node 0.2–3 cm, aggressive histology, vascular invasion, RAI uptake in neck outside thyroid bed, BRAF V600E (if PTC) | 8–22% |
| High | Gross extrathyroidal extension, incomplete tumour resection, distant metastases, postoperative serum thyroglobulin very elevated, N1 node > 3 cm, FTC with extensive vascular invasion | 30–55% |
This is a core comparison table — understand it deeply:
| Feature | Papillary CA | Follicular CA | Medullary CA | Anaplastic CA |
|---|---|---|---|---|
| % of cases | 80–90% | 10–20% | ~5–7% | ~3–5% |
| Cell of origin | Follicular epithelial | Follicular epithelial | Parafollicular C cells | Follicular epithelial (de-differentiated) |
| Age | 30–50y | 40–60y | > 50y (sporadic); 20–30y (familial) | 60–70y |
| Histology | Orphan Annie eye nuclei (clear, ground-glass), nuclear pseudoinclusions, papillary architecture, psammoma bodies (microcalcifications on USG) | Capsular/vascular invasion required to distinguish from follicular adenoma, Hürthle cell variant = worse prognosis | Amyloid deposits (Congo red stain positive) derived from calcitonin; sheets of C cells | Small blue round cells; highly pleomorphic; giant cells; high mitotic index |
| Number | 70% multicentric | Usually solitary | Unilateral (sporadic) vs bilateral multicentric (familial) | Usually single large mass |
| Spread | Lymphatic predilection → 80% associated with cervical LNs (usually Level VI) | Haematogenous predilection → liver, lung, bone, brain | Lymphatic (early nodal and distant mets) | Lymphatic and haematogenous (aggressive) |
| Distant mets | 2–10%: lungs, bones | 10–15%: bone (lytic lesions), lungs | Lungs, liver, bone | Usually locally advanced at presentation |
| Tumour markers | Thyroglobulin (post-op surveillance) | Thyroglobulin | Calcitonin (95%), CEA (80%) | None reliable |
| RAI uptake | Positive (exploitable for Dx and Tx) | Positive | Negative (C cells don't take up iodine) | Negative (de-differentiated, lost NIS) |
| Prognosis | Excellent (10y survival > 95%) | Good (10y survival ~85%) | Moderate (5y survival 60–70%) | Dismal (median survival < 6 months) |
7.1 Mnemonics
Papillary CA — "Popular P's" [1]:
- Popular (most common)
- Palpable LNs
- Positive ¹³¹I uptake
- Positive prognosis
- Post-op ¹³¹I to guide treatment
- Psammoma bodies
Follicular CA — "F's" [1]:
- Female predilection (3:1)
- Far away metastasis (lungs, bones)
- FNAC cannot diagnose (need histology)
- Favourable prognosis
Medullary CA — "M's" [1]:
- MEN2a or 2b
- aMyloid deposits (calcitonin) in histology
- Median node dissection routinely required
8. Clinical Features
| Symptom | Pathophysiological Basis | Type/Stage Association |
|---|---|---|
| Palpable neck lump (thyroid nodule) | Tumour mass in the thyroid gland; most common presenting complaint. Most thyroid nodules are asymptomatic and found incidentally | All types; often the ONLY presenting feature in early DTC |
| Rapidly enlarging neck mass | Rapid cell proliferation (anaplastic, lymphoma) or haemorrhage into a nodule; rapid growth over weeks to months suggests aggressive histology | Anaplastic CA (over 2–3 months), lymphoma, haemorrhage into cyst |
| Pain in the neck | Tumour invading perithyroidal tissues or capsule distension; also haemorrhage into cyst, subacute thyroiditis | Less common in DTC (usually painless); pain suggests aggressive behaviour |
| Hoarseness (dysphonia) | Invasion of the recurrent laryngeal nerve (RLN) → ipsilateral vocal cord paralysis → breathy, hoarse voice. The RLN runs in the tracheo-oesophageal groove directly posterior to the thyroid gland | Locally advanced disease; new-onset hoarseness is a red flag for malignancy [1][3] |
| Dysphagia | Direct invasion or compression of the oesophagus (posterior to the thyroid gland) | Locally advanced disease (especially anaplastic) |
| Dyspnoea / stridor | Invasion or compression of the trachea. Stridor indicates critical airway narrowing (usually > 50% luminal compromise) | Locally advanced, retrosternal extension, anaplastic |
| Cervical lymphadenopathy | Lymphatic metastasis to cervical lymph nodes (especially Level VI central compartment → then lateral Levels III–V). May present as the chief complaint, especially in young patients with PTC where the primary tumour is small | Very common in PTC (80% have nodal involvement) [1]; less common in FTC (8–13%) [1] |
| Symptoms of distant metastases | Bone pain / pathological fractures (bone mets, especially FTC — lytic lesions), cough / haemoptysis / dyspnoea (lung mets, especially PTC), headache / neurological deficits (brain mets, rare) | FTC > PTC for distant mets; FTC has haematogenous predilection |
| Diarrhoea / flushing | In MTC: calcitonin and other peptides (e.g. prostaglandins, serotonin) secreted by the tumour cause secretory diarrhoea and flushing. This is essentially a neuroendocrine tumour syndrome | Medullary thyroid carcinoma (advanced disease) |
| Constitutional symptoms | Weight loss, anorexia, fatigue — indicate advanced/disseminated disease | Anaplastic CA, advanced MTC |
| Sign | Pathophysiological Basis | Clinical Significance |
|---|---|---|
| Solitary or dominant thyroid nodule | More likely malignant than multiple nodules, though cancer can occur in MNG | Key clinical feature raising suspicion of malignancy [1][3] |
| Firm to hard, non-tender nodule | Desmoplastic reaction (fibrosis) around/within the tumour; calcification (psammoma bodies in PTC) gives a gritty/hard feel | Benign nodules tend to be softer and more compressible |
| Fixation to surrounding tissues | Extrathyroidal extension — tumour invades through the thyroid capsule into strap muscles, trachea, oesophagus, or RLN | Fixed nodule = red flag for malignancy [1][3]; the lump does NOT move with swallowing (unlike benign thyroid nodules which move freely) |
| Cervical lymphadenopathy | Metastatic tumour in lymph nodes; firm, non-tender, may be matted | Especially Level VI (central compartment) — first echelon; also lateral neck (Levels III, IV, V) |
| Vocal cord paralysis (on indirect laryngoscopy) | RLN invasion → unilateral cord paralysis → cord fixed in paramedian position | Pre-operative laryngoscopy is mandatory to document vocal cord function before thyroid surgery |
| Pemberton's sign | Large retrosternal goitre; raising both arms above head → facial plethora, distended neck veins, stridor. Caused by compression of the thoracic inlet structures (SVC, trachea) by the substernal thyroid mass | Suggests retrosternal extension |
| Tracheal deviation | Mass effect of a large thyroid nodule/goitre pushing the trachea to the contralateral side | Visible on inspection / palpable on examination / confirmed on imaging |
| Euthyroid state | Most thyroid cancers do not affect thyroid function — they are non-functional | An important negative finding; hyperthyroidism makes cancer less likely (but does NOT exclude it) |
| Signs of MEN syndrome | In MTC: Phaeochromocytoma (episodic hypertension, sweating, headache), Parathyroid hyperplasia (hypercalcaemia symptoms), Mucosal neuromas (bumpy lips, tongue — MEN2B), Marfanoid habitus (MEN2B) | Must screen for phaeochromocytoma BEFORE any thyroid surgery in suspected MEN2 (catecholamine crisis risk) |
This is a critical clinical approach section — essentially, when you see a thyroid nodule, these features should raise your suspicion [1][3]:
Demographics:
- Male sex: thyroid nodules less common in males but more likely to be malignant [1]
- Age < 14 years or > 70 years: nodules in the 3rd–6th decade are usually benign [1]
Nodule characteristics:
- Solitary or dominant nodule: more likely malignant than in multiple [1]
- Slow but progressive growth (weeks to months), firm/hard consistency, fixation to surrounding tissues [1]
- Pressure symptoms / RLN palsy: indicates rapid growth rate with invasion [1]
- Note: Pressure symptoms can be absent in well-differentiated thyroid carcinoma (because they grow slowly and may not invade early) [1]
- Cervical lymph nodes especially Level VI (first site of metastasis) [1]
History:
- Previous neck irradiation [1][3]
- Family history of thyroid CA: especially medullary (~20% familial), papillary (~5% familial), MEN2 [1][3]
Approach to History Taking for a Thyroid Lump
Systematically cover: (1) The lump itself — onset, duration, growth rate, pain, diffuse vs localised. (2) Thyroid function symptoms — hyper vs hypo. (3) Compressive symptoms — dyspnoea, dysphagia, dysphonia. (4) Risk factors for malignancy — radiation, family history, age/sex. (5) Red flags for aggressive disease — rapid growth, fixation, hoarseness, lymphadenopathy [1][3].
- Inspect from the front: visible lump, scars, skin changes, tracheal deviation.
- Ask the patient to swallow: thyroid lumps move with swallowing (attached to pretracheal fascia). A lump that does NOT move with swallowing is either not thyroid or is a fixed malignant thyroid mass.
- Ask to protrude the tongue: a thyroglossal cyst will move upwards (attached to the foramen cecum via the thyroglossal duct remnant); thyroid lumps do NOT.
- Palpate from behind: assess size, consistency, tenderness, nodularity, fixation, tracheal position.
- Palpate cervical lymph nodes: Levels I–VI systematically.
- Auscultate: bruit (Graves' disease).
- Assess thyroid status: pulse rate, tremor, eye signs, reflexes, skin.
- Pemberton's sign: arms raised above head for 1 minute → look for facial plethora, venous distension, stridor (retrosternal goitre).
- Pre-operative laryngoscopy: document vocal cord function before any thyroid surgery (medico-legal requirement).
Before we dive into the investigation algorithm (which will be covered in the next section), it's worth noting the differential for an anterior neck lump [1]:
| Category | Examples |
|---|---|
| Thyroid enlargement | Benign thyroid nodule (colloid cyst, follicular adenoma), multinodular goitre, thyroid cancer, thyroiditis |
| Lymphadenopathy | Reactive, metastatic (from thyroid, NPC, other H&N cancers), lymphoma |
| Skin lumps | Sebaceous cyst, lipoma, dermoid cyst |
| Congenital | Thyroglossal duct cyst (midline, moves with tongue protrusion), branchial cyst (lateral, anterior to SCM) — more common in paediatric patients |
| Other | Laryngocele, carotid body tumour (chemodectoma), cervical rib |
High Yield Summary
Definition: Malignant neoplasm of the thyroid; most commonly papillary carcinoma (80-90%) from follicular epithelial cells.
Epidemiology (HK): 2.6% of all cancers, 5th most common in females, M:F ~1:3-4, increasing incidence, very low mortality.
Key Risk Factors: Female sex, head/neck irradiation (especially NPC treatment in HK), family history, MEN2 syndrome, FAP (papillary), Hashimoto's (lymphoma), iodine deficiency (follicular).
Molecular: MAPK pathway (RET-RAS-BRAF) is central. BRAF V600E in papillary; RAS/PAX8-PPARγ in follicular; RET germline mutations in familial MTC; TP53 in anaplastic.
Clinical Features — Red Flags for Malignancy: Solitary hard fixed nodule, progressive growth, male sex, age < 14 or > 70, hoarseness (RLN invasion), Level VI lymphadenopathy, prior radiation, FHx.
Papillary CA: Most common, lymphatic spread, psammoma bodies, Orphan Annie nuclei, excellent prognosis.
Follicular CA: Haematogenous spread (bone, lung), FNAC cannot diagnose (need histology for capsular/vascular invasion), good prognosis.
Medullary CA: C-cell origin, calcitonin marker, amyloid on histology, MEN2 association, prophylactic thyroidectomy for RET carriers.
Anaplastic CA: De-differentiated, rapidly lethal (< 6 months), no RAI uptake, palliative management.
Active Recall - Thyroid Cancer (Definition, Epidemiology, Risk Factors, Anatomy, Pathophysiology, Classification, Clinical Features)
[1] Senior notes: Ryan Ho Endocrine.pdf (Sections 1.6, 1.6.1, 1.6.2, pp. 33–38) [2] Senior notes: felixlai.md (Thyroid cancer sections I–V, pp. 991–997) [3] Senior notes: maxim.md (Thyroid cancer overview) [4] Lecture slides: Management of differentiated thyroid carcinoma.pdf; GC 177. A thyroid nodule benign thyroid nodules; thyroid cancer.pdf
Differential Diagnosis of Thyroid Cancer
When you encounter a patient with a thyroid nodule, the fundamental clinical question is: is this malignant or benign? Only ~10–15% of thyroid nodules are malignant [3][5]. The differential diagnosis therefore spans a wide spectrum — from benign nodular disease (the vast majority) to primary thyroid malignancies and even metastatic disease from distant sites. Your job is to systematically narrow the field using clinical features, biochemistry, ultrasound characteristics, and cytology.
Let's organise this logically. A thyroid nodule presents in one of three functional states — hyperthyroid, euthyroid, or hypothyroid — and this immediately helps stratify the differential [3].
| Functional Status | Differential Diagnoses | Key Distinguishing Features |
|---|---|---|
| Hyperthyroid (↓TSH) | Toxic adenoma (hot nodule on scintigraphy), Toxic multinodular goitre (MNG), Graves' disease with coincidental nodule | Hot nodules are rarely malignant → scintigraphy is the key investigation when TSH is suppressed. A hot nodule does NOT require FNAC [2][5] |
| Euthyroid (normal TSH) — most common | Benign: colloid nodule/cyst, follicular adenoma, dominant nodule in MNG, Hashimoto's pseudonodule | Most thyroid nodules are euthyroid and benign. USG + FNAC needed to risk-stratify |
| Malignant: papillary CA, follicular CA, medullary CA, anaplastic CA, lymphoma, metastatic disease | Red flag features (see Section 8.3 in prior notes) should raise suspicion | |
| Hypothyroid (↑TSH) | Hashimoto's thyroiditis (pseudonodule or true nodule within a Hashimoto's gland), iodine deficiency goitre | Hashimoto's is associated with 60× risk of thyroid lymphoma [1] |
10.2 Comprehensive Differential Diagnosis — By Category
| Condition | Key Features | Why It Mimics Cancer |
|---|---|---|
| Colloid nodule / cyst | Most common cause of a thyroid nodule. Arises from accumulation of colloid within a hyperplastic follicle. May undergo cystic degeneration or haemorrhage (→ sudden painful enlargement mimicking malignancy) | Sudden size increase can mimic aggressive cancer; but on USG typically spongiform or purely cystic — very low malignancy risk ( < 3%) [2][5] |
| Follicular adenoma | Benign encapsulated follicular neoplasm. Solitary, well-encapsulated. FNAC shows follicular cells — indistinguishable from follicular carcinoma on cytology | The critical DDx. FNAC reports "follicular neoplasm" (Bethesda IV) — only surgical excision with histological assessment for capsular/vascular invasion can distinguish adenoma from carcinoma [2][3][5] |
| Dominant nodule in MNG | One nodule stands out in a background of multiple nodules. MNG results from cycles of hyperplasia and involution driven by TSH fluctuations | A dominant or growing nodule in MNG still requires the same evaluation as a solitary nodule — cancer can coexist within an MNG [3][5] |
| Hashimoto's thyroiditis (pseudonodule) | Focal lymphocytic infiltration can create a palpable "nodule" within a diffusely inflamed gland. ↑TPO antibodies, hypothyroid. Also predisposes to thyroid lymphoma (60× risk) [1] | Firm, irregular texture can mimic malignancy. USG shows diffusely heterogeneous parenchyma |
| Simple thyroid cyst | True simple cysts (rare, < 2% of nodules) are lined by epithelium and contain clear fluid. Purely cystic nodules have < 1% malignancy risk and do NOT require FNAC [2][5] | Occasional diagnostic dilemma when cysts have a solid component — mixed cystic-solid nodules need further evaluation |
Important Distinction
Follicular adenoma is NOT a risk factor for follicular carcinoma [3]. They are biologically distinct. Do NOT assume that a follicular adenoma "transforms" into carcinoma. However, on FNAC they cannot be distinguished — the Bethesda system reports both as "follicular neoplasm" (Category IV), and surgical excision is required for definitive diagnosis.
| Cancer | Key Differentiating Points |
|---|---|
| Papillary thyroid carcinoma | Most common (80–90%). Young adults 30–50y. Lymphatic spread to Level VI nodes. USG: microcalcifications (psammoma bodies), hypoechoic, irregular margins. FNAC diagnostic: Orphan Annie nuclei, nuclear pseudoinclusions [1][2] |
| Follicular thyroid carcinoma | 10–20%. Middle-aged 40–60y. Haematogenous spread (bone, lung). FNAC cannot distinguish from follicular adenoma — requires histological capsular/vascular invasion [1][2][3] |
| Medullary thyroid carcinoma | 5–7%. C-cell origin. Tumour markers: calcitonin (95%), CEA (80%) [1]. 25% familial (MEN2). Check RET mutation in all MTC patients. Amyloid deposits on histology |
| Anaplastic carcinoma | 3–5%. Elderly 60–70y. Rapidly enlarging hard goitre over 2–3 months. Often locally advanced with distant metastasis at presentation. Median survival < 6 months [1]. May arise from de-differentiation of previous DTC (30%) |
| Thyroid lymphoma | ~1–5%. > 50y, F > M. Strong association with Hashimoto's thyroiditis (60× risk) [1]. Usually diffuse large B-cell lymphoma (DLBCL). Rapidly enlarging goitre with compressive symptoms. Requires core biopsy (NOT FNAC) for diagnosis — FNAC is useless for lymphoma [6] |
| Poorly differentiated (insular) carcinoma | ~5%. Intermediate behaviour between DTC and anaplastic. Meets Turin criteria (solid/trabecular/insular growth pattern, necrosis, high mitotic rate) |
| Squamous cell carcinoma (SCC) of thyroid | Very rare. Usually represents direct extension from adjacent structures (larynx, oesophagus) or metastasis. Must exclude primary elsewhere |
Why can't FNAC diagnose lymphoma? FNAC provides only individual cells (cytology) — it cannot demonstrate the tissue architecture needed for lymphoma classification. Lymphoma diagnosis requires assessment of tissue architecture, immunohistochemistry, and flow cytometry — all of which need a core biopsy or excisional biopsy [6].
The thyroid can be a site of metastatic disease, though this is relatively uncommon clinically:
| Primary Site | Notes |
|---|---|
| Renal cell carcinoma (RCC) | Most common source of metastasis to the thyroid [3]. The thyroid's rich blood supply makes it a target. Can present years after nephrectomy — always ask about RCC history |
| Colorectal carcinoma | Haematogenous spread |
| Lung carcinoma | |
| Breast carcinoma | |
| Melanoma |
Why is RCC the most common metastasis to the thyroid? RCC is known for its propensity for vascular invasion and haematogenous spread to unusual sites ("clear cell metastases"). The thyroid receives ~2% of cardiac output per unit mass — one of the highest blood flows per gram of any organ — making it a favourable "seed" site per the Paget "seed and soil" hypothesis.
Sometimes a neck lump is mistaken for a thyroid nodule. The differential of an anterior neck lump includes [1][5]:
| Category | Condition | Key Distinguishing Feature |
|---|---|---|
| Thyroid | Goitre, nodule, carcinoma | Moves with swallowing (attached to pretracheal fascia) |
| Lymphadenopathy | Reactive, metastatic (NPC, H&N SCC), lymphoma | Does NOT move with swallowing; may be hard/fixed/matted |
| Thyroglossal duct cyst | Congenital remnant of thyroglossal duct (from foramen cecum to thyroid) | Midline, moves upward on tongue protrusion (pathognomonic). Usually paediatric. |
| Branchial cyst | Remnant of branchial apparatus | Lateral, anterior to SCM. Usually paediatric/young adult. Does not move with swallowing |
| Skin | Sebaceous/epidermoid cyst, lipoma, dermoid | Superficial, moves with skin, not attached to deeper structures |
| Other | Laryngocele, carotid body tumour (chemodectoma), pharyngeal pouch | Specific examination findings (e.g. Fontaine's sign for carotid body tumour — mobile side-to-side but not up-and-down; pulsatile) |
The clinical approach starts with the presenting complaint (usually a thyroid nodule or neck lump) and moves through a logical decision tree. Here is the framework:
This is conceptually part of diagnosis (covered fully in the next section), but understanding which investigation helps discriminate which differential is essential here:
| Investigation | What It Tells You | Key Differentiating Power |
|---|---|---|
| TFT (TSH) | TSH is the MOST sensitive indicator of thyroid function [2]. A suppressed TSH suggests a functioning (hot) nodule — which is almost never cancer | Separates hot nodules (benign) from cold/neutral nodules (need further workup) |
| Thyroid USG | Characterises nodule architecture, echogenicity, calcifications, margins, vascularity; assesses cervical lymph nodes | Sonographic features suspicious of malignancy ("SHIT CME"): Solid, Hypoechoic, Irregular margins, Taller than wide, Chaotic central vascularity, Microcalcifications, Extrathyroidal extension [3][5] |
| FNAC (USG-guided) | Cytological assessment — the gold standard for pre-operative diagnosis of thyroid nodules. Reported using Bethesda classification (6 categories) [2][3][5] | Diagnostic for papillary CA (Orphan Annie nuclei, psammoma bodies), medullary CA (amyloid deposits, calcitonin immunostain); CANNOT distinguish follicular adenoma from follicular carcinoma [2][3] |
| Thyroid scintigraphy | Determines functional status: hot (↑uptake) vs cold (↓uptake) vs warm (= surrounding) | Hot nodules are rarely cancer and do NOT need FNAC [2][5]. Cold nodules have 10–20% risk of malignancy and require FNAC [2] |
| Serum calcitonin | Produced by C cells; elevated in MTC | Raised calcitonin ( > 100 pg/mL) = high suspicion for MTC. Important to check in patients with FHx of MTC or MEN2 [1][2] |
| Serum thyroglobulin | Produced by follicular cells; used as tumour marker for DTC post-operatively | NOT useful pre-operatively for differential diagnosis (elevated in many benign thyroid conditions). Useful only after total thyroidectomy as a marker of recurrence [2] |
| Core biopsy / excisional biopsy | Tissue architecture — essential for lymphoma diagnosis | Required when lymphoma is suspected — FNAC alone is insufficient [6] |
This is a common exam scenario. The differential for sudden increase in size of a thyroid lump [1][5]:
| Cause | Mechanism | Key Clue |
|---|---|---|
| Haemorrhage into a cyst or necrotic nodule | Intra-nodular bleeding → sudden capsular distension → acute pain and swelling | Sudden onset, pain, tender, pre-existing nodule. USG shows internal haemorrhagic content. Resolves with aspiration |
| Anaplastic carcinoma | Explosive undifferentiated cell proliferation | Elderly patient, rock-hard, fixed, rapidly enlarging over weeks. Compressive symptoms. Very poor prognosis |
| Primary thyroid lymphoma | Rapid lymphoid cell proliferation in a background of Hashimoto's thyroiditis | History of Hashimoto's, rapidly enlarging firm mass, compressive symptoms. Needs core biopsy |
| Subacute (de Quervain's) thyroiditis | Post-viral inflammatory destruction of follicles | Painful, tender, febrile, ↑ESR, preceding URTI. Self-limiting. Fluctuating thyroid status |
| Feature | Favours Benign | Favours Malignant |
|---|---|---|
| Demographics | Female, 30–60y | Male, age < 14 or > 70 [1][5] |
| Number | Multiple nodules (MNG) | Solitary or dominant [1][5] |
| Consistency | Soft, rubbery, compressible | Hard, firm, gritty |
| Mobility | Freely mobile with swallowing | Fixed to surrounding structures [1][5] |
| Growth rate | Stable or very slow | Progressive growth over wks–months [1][5] |
| Pain | Painful (haemorrhagic cyst, thyroiditis) | Usually painless (except anaplastic, lymphoma) |
| Cervical LN | Absent | Present, especially Level VI [1][5] |
| Voice | Normal | Hoarseness (RLN invasion) [1][5] |
| TSH | Suppressed (hot nodule) | Normal or elevated |
| USG | Spongiform, purely cystic, comet-tail artefact, hyperechoic | Hypoechoic, microcalcifications, taller-than-wide, irregular margins, central vascularity, extrathyroidal extension [3][5] |
| Scintigraphy | Hot nodule | Cold nodule |
| FNAC | Bethesda II (benign) | Bethesda V–VI |
| History | No radiation, no FHx | Radiation exposure, FHx thyroid CA, MEN2 [1][5] |
This is a common clinical dilemma and a high-yield exam topic:
- Bethesda III (AUS/FLUS — Atypia of Undetermined Significance / Follicular Lesion of Undetermined Significance): Cancer risk ~10–30%. Management: repeat FNAC, or increasingly molecular testing (e.g. ThyroSeq v3 genomic classifier, Afirma gene expression classifier) to help "rule in" or "rule out" malignancy and avoid unnecessary surgery [2][5].
- Bethesda IV (Follicular Neoplasm / Suspicious for Follicular Neoplasm): Cancer risk ~25–40%. FNAC cannot distinguish follicular adenoma from follicular carcinoma because the distinction rests on capsular/vascular invasion (architectural, not cytological). Management: diagnostic hemithyroidectomy (lobectomy) [2][3][5].
Why does Bethesda IV exist as a separate category? Because the cytological features of follicular adenoma and follicular carcinoma are identical — both show microfollicular architecture with scant colloid. Only by examining the intact capsule histologically can you determine if the tumour has invaded through it. This is a fundamental limitation of needle aspiration cytology.
Molecular Testing — The Modern Approach
In the 2020s, molecular testing (e.g. ThyroSeq v3, Afirma GSC) is increasingly used for Bethesda III–IV nodules to reduce the rate of diagnostic surgery. A benign molecular result has a high negative predictive value ( > 95%), allowing observation instead of lobectomy. This is not yet standard practice in all Hong Kong centres but is increasingly adopted in tertiary settings.
High Yield Summary
DDx framework: Organise by functional status (hyperthyroid → think hot nodule/toxic adenoma; euthyroid → most common, benign vs malignant; hypothyroid → Hashimoto's ± lymphoma risk).
Most thyroid nodules are benign (~85–90%): colloid cyst, follicular adenoma, MNG, Hashimoto's pseudonodule.
Primary thyroid malignancies: Papillary (most common, lymphatic spread, psammoma bodies), Follicular (haematogenous, FNAC cannot diagnose), Medullary (C-cells, calcitonin, MEN2), Anaplastic (rapidly lethal, de-differentiated), Lymphoma (Hashimoto's background, needs core biopsy).
Metastatic to thyroid: RCC is the most common primary.
Red flags for malignancy: Male, age extremes, solitary hard fixed nodule, hoarseness, Level VI LN, radiation history, FHx, cold on scintigraphy, SHIT CME on USG.
Critical DDx pitfall: Follicular adenoma vs carcinoma — indistinguishable on FNAC; requires surgical excision for histological capsular/vascular invasion.
Rapidly enlarging thyroid: DDx = haemorrhagic cyst, anaplastic CA, thyroid lymphoma, subacute thyroiditis.
Hot nodule on scintigraphy: Rarely malignant → does NOT need FNAC.
Active Recall - Differential Diagnosis of Thyroid Cancer
References
[1] Senior notes: Ryan Ho Endocrine.pdf (Sections 1.6, 1.6.1, 1.6.2, pp. 33–38) [2] Senior notes: felixlai.md (Thyroid cancer sections I–IX, pp. 991–1007) [3] Senior notes: maxim.md (Thyroid cancer overview, Approach to thyroid nodules) [4] Lecture slides: Management of differentiated thyroid carcinoma.pdf [5] Senior notes: Ryan Ho Fundamentals.pdf (pp. 426–427); Ryan Ho Endocrine.pdf (pp. 18–19) [6] Senior notes: Ryan Ho Haemtology.pdf (p. 87 — approach to lymphadenopathy and biopsy methods)
Diagnostic Criteria, Diagnostic Algorithm, and Investigation Modalities
Unlike many cancers, thyroid cancer does not have a single "diagnostic criterion" in the way that, say, rheumatoid arthritis has classification criteria. Instead, the diagnosis is built through a stepwise investigative algorithm that progresses from clinical suspicion → biochemistry → imaging → cytology → histology. The definitive diagnosis is almost always histopathological — either on FNAC (for papillary and medullary CA) or on surgical specimen (for follicular CA, where architectural invasion must be demonstrated).
Let's think about this from first principles: you cannot biopsy every thyroid nodule (they are incredibly common — ~50% of adults have thyroid nodules on ultrasound), so the investigative pathway is designed as a risk-stratification funnel that filters out the majority of benign nodules and triages the suspicious ones for tissue diagnosis [1][3][5][7].
11.3 Investigation Modalities — Detailed Breakdown
A. Blood Tests (Biochemistry)
- TSH level is the MOST sensitive indicator of thyroid function due to its short half-life and the log-linear relationship with fT4 (small changes in fT4 cause large changes in TSH) [2].
- Purpose: The FIRST blood test ordered. It determines the functional status of the thyroid and guides the next step.
- Important: Most thyroid cancers are euthyroid — they do NOT produce excess thyroid hormone. Therefore a normal TSH does not exclude malignancy.
- Elevated TSH is associated with increased thyroid cancer risk in patients with thyroid nodules [2] — higher TSH provides more trophic stimulation to follicular cells.
Exam Pitfall
A common mistake is to order thyroid scintigraphy for every thyroid nodule. Scintigraphy is ONLY indicated when TSH is suppressed (hyperthyroid), to determine if the nodule is hot or cold. It is NOT recommended for routine diagnostic use in euthyroid patients because the nodule will never be hyperfunctioning in that setting, and you would need USG ± FNAC regardless [2][5][7].
- Why? Two reasons [2][3]:
- Hypercalcaemia of malignancy — some aggressive thyroid cancers or concurrent MEN-related parathyroid hyperplasia can cause raised calcium.
- Baseline pre-operative value — after thyroidectomy, hypoparathyroidism is a major complication (inadvertent removal/devascularisation of parathyroid glands → hypocalcaemia). You need a pre-op baseline.
- Anti-thyroglobulin (TG) antibodies should be measured to assess whether thyroglobulin can be used as a tumour marker for recurrence after total thyroidectomy [2].
- Why? Anti-TG antibodies interfere with the thyroglobulin assay, causing falsely low readings. If anti-TG antibodies are positive, serum thyroglobulin becomes unreliable as a surveillance marker. In such cases, anti-TG antibody levels themselves are followed as a surrogate marker (rising titres suggest recurrence).
- Anti-TPO antibodies: if Hashimoto's thyroiditis is suspected (background for thyroid lymphoma).
- Baseline tumour marker for differentiated thyroid carcinoma (DTC) [2].
- Thyroglobulin is a glycoprotein produced exclusively by thyroid follicular cells. After total thyroidectomy + RAI ablation, Tg should become undetectable — any subsequent rise indicates recurrence or residual disease.
- NOT useful pre-operatively for distinguishing benign from malignant (Tg is elevated in many benign thyroid conditions including goitre, thyroiditis).
- NOT appropriate for patients who have had only hemithyroidectomy (remaining lobe produces Tg) or those with detectable anti-TG antibodies [2].
- Baseline tumour marker for medullary thyroid carcinoma (MTC) — 95% of MTC produces calcitonin [1][2][7].
- When to order: If there is history or clinical suspicion of familial medullary carcinoma or MEN2 [1][5].
- Interpretation: Basal calcitonin > 100 pg/mL is highly suggestive of MTC. If calcitonin > 500 pg/mL, consider metastatic disease → proceed to staging with CT thorax/abdomen/pelvis and bone scan [3].
- Calcitonin can also be used as a stimulated test (pentagastrin or calcium stimulation) for borderline cases.
- All patients with MTC should be tested for RET mutation [1][2][7].
- Why? ~25% of MTC is familial (MEN2A, MEN2B, isolated familial MTC) — all caused by germline RET proto-oncogene mutations. Identifying the mutation has profound implications:
- Molecular testing on FNAC specimens (e.g. ThyroSeq v3, Veracyte Afirma gene expression classifier): increasingly used for Bethesda III–IV indeterminate nodules to improve risk stratification and reduce unnecessary diagnostic surgery [1][5]. Currently expensive, no universal standards, and not readily available in all centres [1][5].
- Baseline haematological assessment. Also relevant if thyroid lymphoma is in the differential [2].
Pre-operative Workup for MTC — Checklist
Rule out familial disease (25% of MTC): family history, RET mutation analysis. Rule out phaeochromocytoma: 24h urine metanephrines (MUST do BEFORE surgery — risk of catecholamine crisis). Tumour markers: calcitonin, CEA. Ca²⁺ and PTH: to detect parathyroid hyperplasia in MEN2A. Staging if calcitonin > 500: CT chest/abdomen/pelvis + bone scan [3].
B. Imaging
USG is routine for ALL patients with goitre or palpable nodules [1][3][5][7].
| Aspect | Detail |
|---|---|
| Technique | 7.5 or 10 MHz probes, B-mode [1][5]. High-frequency linear probe provides excellent resolution for superficial structures |
| Pros | Readily available, non-invasive, high sensitivity [1][5] |
| Cons | Low specificity — many benign nodules have "suspicious" features; NOT a screening test for healthy subjects [1][5] |
| Role | Extension of physical examination to guide (not confirm) diagnosis; risk-stratify nodules for selective FNAC [1][5] |
What to assess on USG [1][2][5]:
The nodule itself:
| Feature | High Risk (Suspicious) | Low Risk (Reassuring) | Pathophysiological Basis |
|---|---|---|---|
| Echogenicity | Hypoechoic | Hyperechoic or isoechoic | Malignant cells are densely packed with high nuclear:cytoplasmic ratio → less acoustic reflection → hypoechoic |
| Calcifications | Microcalcifications ( < 0.2 mm) | Large coarse calcifications | Microcalcifications represent psammoma bodies in papillary CA — concentric laminated calcific deposits from dystrophic calcification of papillary tips [1][2][5] |
| Shape | Taller than wide (AP > TS) | Wider than tall | Growth perpendicular to tissue planes suggests aggressive infiltration across normal tissue boundaries |
| Margins | Irregular (infiltrative, microlobulated) | Smooth, well-defined | Irregular margins indicate invasive growth through the capsule |
| Internal structure | Solid, or cystic with irregular septa | Spongiform (sponge-like microcystic), purely cystic | Solid components raise malignancy risk; spongiform pattern is ~99% benign |
| Halo (perilesional rim) | Absent or incomplete halo | Complete halo | The halo represents compressed thyroid parenchyma around a benign encapsulated nodule. Absence suggests lack of capsule (invasive) |
| Vascularity | Central/intranodular | Peripheral | Intranodular vascularity indicates tumour neoangiogenesis; peripheral vascularity reflects compression of normal peri-capsular vessels |
| Extrathyroidal extension | Present | Absent | Direct invasion beyond the thyroid capsule into strap muscles, trachea, etc. |
Mnemonic for suspicious USG features: "SHIT CME" [3]: Solid, Hypoechoic, Irregular margins, Taller than wide, Chaotic central vascularity, Microcalcifications, Extrathyroidal extension. The most important features are solid and hypoechoic [3].
Surrounding structures:
| Feature | What to Look For |
|---|---|
| Other nodules | Multiple nodules suggest MNG (somewhat reassuring, but a dominant nodule still needs evaluation) |
| Parenchymal abnormalities | Diffuse heterogeneity, reduced echogenicity → suggests thyroiditis (Hashimoto's) |
| Cervical lymph nodes | Sonographic features of malignant LN: Large > 2 cm, Roundish (taller than wide), Heterogeneous hypoechoic, Loss of central fatty hilum, Microcalcification, Intranodal cystic or coagulative necrosis [2][5] |
| Retrosternal extension | Lower border of the thyroid not visible below the clavicle → need CT for further assessment |
Sonographic Criteria for FNAC (ATA 2015 / ACR TI-RADS):
The ATA 2015 table describes the pattern of the nodule. The ACR TI-RADS table converts USS features into a numbered score (TR1–TR5) and gives a concrete action: no biopsy, ultrasound follow-up, or FNAC.
| Sonographic Pattern | Ultrasound Findings | Risk of Malignancy | Size Cutoff for FNA |
|---|---|---|---|
| High suspicion | Solid hypoechoic nodule (OR) solid hypoechoic component of partially cystic nodule + ≥ 1 of: microcalcifications, rim calcification with extrusive soft tissue, taller-than-wide, irregular margins, extrathyroidal extension | > 70–90% | ≥ 1 cm |
| Intermediate suspicion | Hypoechoic solid nodule WITHOUT microcalcifications, taller-than-wide, or extrathyroidal extension | 10–20% | ≥ 1 cm |
| Low suspicion | Isoechoic or hyperechoic nodule, partially cystic with eccentric solid area WITHOUT suspicious features | 5–10% | ≥ 1.5 cm |
| Very low suspicion | Spongiform nodules, partially cystic WITHOUT high/intermediate/low features | < 3% | ≥ 2 cm (or observe) |
| Benign | Purely cystic nodules with no solid component | < 1% | NO FNA |
ACR TI-RADS (2017) — what to do with each numbered category [9]:
| ACR TI-RADS Category | Points | Meaning | FNAC threshold | USS follow-up threshold / schedule |
|---|---|---|---|---|
| TR1 | 0 | Benign | No FNAC | No routine ACR follow-up |
| TR2 | 2 | Not suspicious | No FNAC | No routine ACR follow-up |
| TR3 | 3 | Mildly suspicious | ≥ 2.5 cm | ≥ 1.5 cm: USS at 1, 3, and 5 years |
| TR4 | 4–6 | Moderately suspicious | ≥ 1.5 cm | ≥ 1.0 cm: USS at 1, 2, 3, and 5 years |
| TR5 | ≥ 7 | Highly suspicious | ≥ 1.0 cm | ≥ 0.5 cm: annual USS up to 5 years |
Practical rule: biopsy the highest TI-RADS scoring nodules that meet size criteria, not simply the largest nodules. In multinodular thyroids, ACR recommends sampling no more than two nodules that meet FNAC criteria and following no more than four nodules that meet follow-up criteria [9].
Key Principle
The entire USG → FNAC pathway is a risk-stratification tool, not a diagnostic test. USG cannot definitively diagnose or exclude thyroid cancer — it identifies nodules that warrant tissue sampling. ACR TI-RADS is especially useful when a report gives a TR number: TR1–2 = no FNAC; TR3–5 = follow size thresholds for follow-up vs FNAC. The definitive pre-operative diagnosis comes from FNAC cytology (Bethesda classification).
FNAC is the single most important investigation for a thyroid nodule when TSH is not suppressed [1][5].
| Aspect | Detail |
|---|---|
| Technique | Trans-isthmic approach ± USG guidance. USG guidance confirms presence of nodule and targets biopsy to the most suspicious region [1][5] |
| Accuracy | 90–95% → can avoid unnecessary diagnostic thyroidectomy [1][5] |
| Pros | Minimally invasive, safe, high diagnostic yield, outpatient procedure |
| Cons | Cannot demonstrate capsular or vascular invasion → cannot distinguish follicular adenoma from follicular carcinoma [1][2][3][5]. Also cannot diagnose lymphoma (needs core biopsy for architecture) |
| Complications | Pain, bleeding, false negative (especially in cystic nodules where the solid component is missed) |
Core needle biopsy is NOT routinely performed on the thyroid because the thyroid is a very vascularised structure and core biopsy would lead to massive bleeding. FNAC is very accurate in identifying the type of thyroid cancer [2].
Indications for FNAC [2][5][7]:
- Meets sonographic criteria for FNA (see table above)
- Hypofunctioning (cold) nodules on thyroid scintigraphy (10–20% malignancy risk)
- Dominant or atypical nodule in multinodular goitre
- Nodules associated with abnormal lymph nodes
- Complex or recurrent cystic nodules
- Symptomatic or large cysts (also therapeutic — aspiration decompresses)
- Can proceed directly to total thyroidectomy if > 4 cm, gross invasion, or LN positive (FNAC may not change management) [1]
This is the universal standardised reporting system for thyroid FNAC [2][7]:
| Bethesda Category | Diagnostic Category | Risk of Malignancy (%) | Usual Management |
|---|---|---|---|
| I | Non-diagnostic / Unsatisfactory | 1–4% | Repeat FNA (or surgery if radiologically suspicious) |
| II | Benign | 0–3% | Clinical follow-up (repeat USG in 12–24 months) |
| III | Atypia of undetermined significance (AUS) OR Follicular lesion of undetermined significance (FLUS) | 5–15% | Repeat FNA, molecular testing, or hemithyroidectomy if AUS × 2 |
| IV | Follicular neoplasm / Suspicious for follicular neoplasm | 15–30% | Diagnostic hemithyroidectomy (± molecular testing) |
| V | Suspicious for malignancy | 60–75% | Hemithyroidectomy + frozen section → total thyroidectomy |
| VI | Malignant | 97–99% | Total thyroidectomy |
Cytological findings by cancer type:
| Cancer Type | Cytological Features on FNAC |
|---|---|
| Papillary CA | Orphan Annie eye nuclei (empty, ground-glass appearance with nuclear clearing), nuclear pseudoinclusions (cytoplasmic invaginations into the nucleus), papillary architecture, psammoma bodies (laminated calcified structures), nuclear grooves [1][2] |
| Follicular CA | Follicular structures similar to normal thyroid — microfollicular pattern with scant colloid. Cannot differentiate follicular adenoma from carcinoma on FNAC because diagnosis of carcinoma relies on capsular or vascular invasion which is not appreciated on FNAC due to limited architectural information [2][3] |
| Medullary CA | Distinctive deposits of acellular amyloid material (from altered calcitonin aggregation), plasmacytoid cells, positive calcitonin immunostaining. Multicentric C-cell hyperplasia in familial cases [2] |
| Anaplastic CA | Small blue round cells that are highly anaplastic, marked pleomorphism, bizarre giant cells, necrosis, high mitotic figures [2] |
| Lymphoma | Lymphoid cells on FNAC — FNAC cannot diagnose lymphoma → need core biopsy for tissue architecture, immunohistochemistry, and flow cytometry |
Why are "Orphan Annie" nuclei called that? They are named after the cartoon character Little Orphan Annie, whose eyes appeared blank and empty. In papillary thyroid carcinoma, the nuclear clearing on haematoxylin and eosin (H&E) staining creates this characteristic "empty" appearance due to dispersal of chromatin to the nuclear periphery during tissue fixation.
Frozen Section — Is It Useful?
Frozen section (FS) is NOT helpful in hemithyroidectomy for follicular neoplasm (Bethesda IV). It only gives diagnostic information in ~13% of cases and modifies the surgical procedure in only 3.3%, with misguided intervention in 5% [1][5]. One should wait for the final histology report after lobectomy. If it shows encapsulated minimally invasive FTC ( < 5 vessel invasion, no wide invasion), lobectomy is curative. Otherwise, completion thyroidectomy + RAI ablation is needed [1][5].
However, FS is useful for Bethesda V (suspicious for malignancy) — if FS confirms malignancy intra-operatively, the surgeon can proceed directly to total thyroidectomy in the same operation, avoiding a second surgery.
| Aspect | Detail |
|---|---|
| Radiopharmaceuticals | ⁹⁹ᵐTc pertechnetate (iodine trapping only — has similar ionic size to iodide, taken up by NIS), ¹²³I or ¹³¹I (trapping + organification) [8] |
| Principle | Radioactive iodine is handled in the same manner as normal iodine. Level of uptake reflects metabolic activity [8] |
| Images | Anterior, left anterior oblique (LAO), and right anterior oblique (RAO) views [8] |
- ONLY in patients with a thyroid nodule AND suppressed TSH (↓TSH) → to determine if the nodule is hot or cold
- NOT recommended for routine diagnostic use in euthyroid patients [2][7]
- Also indicated in multinodular goitre (MNG) to determine functional status of different nodules
Interpretation:
| Scintigraphic Finding | Definition | Clinical Significance |
|---|---|---|
| Hot nodule (hyperfunctioning) | Uptake greater than surrounding thyroid tissue | Almost never malignant → does NOT require FNAC. Treat as toxic adenoma [2][5][7] |
| Cold nodule (hypofunctioning) | Uptake less than surrounding thyroid tissue | 10–20% risk of malignancy → requires FNAC provided sonographic criteria are met [2][5][7] |
| Warm nodule (indeterminate) | Uptake similar to surrounding tissue | Intermediate risk; proceed based on USG features |
Why is scintigraphy NOT done when TSH is normal or elevated? Because a euthyroid or hypothyroid patient's nodule will never be "hot" — by definition, a hot nodule suppresses TSH via autonomous hormone production. If TSH is normal, the nodule is not autonomously functioning, and scintigraphy provides no additional discriminatory information beyond what USG + FNAC can give [2].
Clinical indications for thyroid scintigraphy [8]:
- Assessment of thyroid nodules, goitre, organification defect, thyroid cancer
- Evaluation of ectopic thyroid
- Diagnosis of causes of thyrotoxicosis or hypothyroidism
- Post-surgery or radiotherapy assessment of residual thyroid gland
| Aspect | Detail |
|---|---|
| Indications | NOT routine — only when: (1) retrosternal goitre (cannot be visualised by USG, needed for surgical planning), (2) locally advanced thyroid cancer (delineation of important structures within cervical fascia), (3) staging for distant mets [1][2][3][5] |
| CT thorax | Determine extent of retrosternal goitre or thyroid tumour; identify tumour invasion of great vessels and upper aerodigestive tract [2] |
| MRI | Better soft tissue contrast than CT; useful for assessing extent of local invasion (trachea, oesophagus, carotid sheath) |
Contrast CT Warning
The use of iodinated contrast in CT may affect post-operative radioactive iodine (RAI) whole-body scan and therapy [1][5]. Iodine contrast "loads" the body with stable iodine, which competes with ¹³¹I for uptake by residual thyroid/tumour tissue, reducing the efficacy of both diagnostic scanning and therapeutic RAI. A delay of 4–8 weeks after iodinated contrast is recommended before RAI. Plan imaging accordingly!
- Tracheal deviation (mass effect of large goitre/tumour)
- Mediastinal shadow for retrosternal extension
- Lung metastases (cannonball or miliary pattern — especially in follicular CA with haematogenous spread) [2]
- No role in routine primary diagnosis of thyroid cancer [3]
- Used for:
- Staging of aggressive thyroid cancers (anaplastic, poorly differentiated)
- Radioiodine-refractory DTC — FDG-avid tumour that does NOT take up ¹³¹I (the "flip-flop" phenomenon: as tumours de-differentiate, they lose NIS expression → ↓RAI uptake, but gain GLUT-1 expression → ↑FDG uptake)
- Detection of recurrence when thyroglobulin is rising but RAI whole-body scan is negative
| Modality | Indication | Finding |
|---|---|---|
| Direct laryngoscopy | Pre-operative assessment of vocal cord function (RLN status) — mandatory before thyroid surgery [1][5] | Documents pre-existing vocal cord paralysis (from tumour invasion of RLN vs pre-existing pathology) |
| Bronchoscopy | Invasion into trachea — if airway involvement suspected (stridor, haemoptysis) [2] | Mucosal involvement, intraluminal tumour |
| OGD (oesophagogastroduodenoscopy) | Invasion into oesophagus — if dysphagia suggests oesophageal involvement [1][2][5] | Extrinsic compression or mucosal invasion |
11.4 Staging Systems
Once thyroid cancer is diagnosed, staging determines prognosis and guides post-operative management.
T Staging (Tumour):
| Stage | Criteria |
|---|---|
| T1 | Tumour ≤ 2 cm, limited to thyroid |
| T1a | Tumour ≤ 1 cm |
| T1b | Tumour > 1 cm and ≤ 2 cm |
| T2 | Tumour > 2 cm but ≤ 4 cm, limited to thyroid |
| T3 | Tumour > 4 cm limited to thyroid, OR gross extrathyroidal extension invading only strap muscles |
| T3a | Tumour > 4 cm limited to thyroid |
| T3b | Gross extrathyroidal extension invading only strap muscles |
| T4 | Gross extrathyroidal extension beyond strap muscles |
| T4a | Invading subcutaneous soft tissues, larynx, trachea, oesophagus, or RLN |
| T4b | Invading prevertebral fascia or encasing carotid artery or mediastinal vessels |
Specifier: (s) = solitary tumour; (m) = multifocal tumour [1]
N Staging (Nodes):
| Stage | Criteria |
|---|---|
| N1a | Level VI and/or Level VII nodes (central compartment) |
| N1b | Level I–V nodes (lateral compartment) |
Overall Stage Grouping — Differentiated Thyroid Cancer (PTC, FTC):
| Age < 55 years | Age ≥ 55 years | |
|---|---|---|
| Stage I | Any T, Any N, M0 | T1–T2, N0, M0 |
| Stage II | Any T, Any N, M1 | T1–T2, N1, M0 / T3, Any N, M0 |
| Stage III | — | T4a, Any N, M0 |
| Stage IVA | — | T4b, Any N, M0 |
| Stage IVB | — | Any T, Any N, M1 |
Key point: Age < 55 years → maximum Stage II even with distant metastases. This reflects the remarkably good prognosis of differentiated thyroid cancer in young patients (5-year survival > 98% even with M1 disease). Anaplastic carcinoma is automatically Stage IV regardless of extent [1][3].
- M — Metastasis
- A — Age
- C — Completeness of resection
- I — Invasion (extrathyroidal extension)
- S — Size
Covered in detail in Section 6.3 of prior notes. This is used post-operatively to guide the intensity of adjuvant therapy (RAI ablation) and surveillance.
Here is how a clinician should approach a thyroid nodule, step by step:
| Step | Action | Rationale |
|---|---|---|
| 1 | History + Physical Examination | Identify red flags for malignancy (Section 8.3) |
| 2 | TFT (TSH ± fT4) — FIRST blood test | Determine functional status; suppressed TSH → scintigraphy [1][5][7] |
| 3 | Thyroid USG — ROUTINE for ALL | Risk-stratify the nodule; assess cervical LNs; guide FNAC [1][3][5][7] |
| 4 | Thyroid scintigraphy — ONLY if TSH suppressed | Hot nodule = benign (no FNAC needed); cold nodule → FNAC [2][5][7] |
| 5 | USG-guided FNAC — for suspicious nodules meeting size criteria | Bethesda classification guides management [1][2][5][7] |
| 6 | Bethesda I–II → Follow-up; III → Repeat or molecular test; IV–VI → Surgery | See Bethesda table above |
| 7 | If malignancy confirmed/suspected → Pre-operative workup | CT neck/chest (if locally advanced), direct laryngoscopy (vocal cord function), tumour markers (Tg, calcitonin, CEA), Ca/PO₄, genetic testing if MTC |
| 8 | Post-operative → Histopathology → TNM staging + ATA risk stratification | Determines need for completion thyroidectomy, RAI, TSH suppression |
Routine for ALL patients: History, PE, TFT, thyroid USG ± FNAC [3].
Selective investigations (not routine): [3]
- Thyroid scintigraphy: only if TSH suppressed + nodule
- CT scan: only if retrosternal goitre or locally advanced cancer
- PET scan: no diagnostic role — only for staging aggressive/RAI-refractory disease
High Yield Summary
Investigation hierarchy: TFT (TSH) → USG → FNAC (± scintigraphy if TSH suppressed).
TSH is the first test: Suppressed → scintigraphy; Normal/elevated → USG ± FNAC directly.
USG suspicious features (SHIT CME): Solid, Hypoechoic, Irregular margins, Taller-than-wide, Chaotic central vascularity, Microcalcifications, Extrathyroidal extension.
FNAC is the single most important investigation: Bethesda classification guides management. Cannot diagnose follicular CA (need histological capsular/vascular invasion). Cannot diagnose lymphoma (need core biopsy).
Hot nodule on scintigraphy = almost never malignant → NO FNAC needed. Cold nodule = 10–20% malignancy risk → needs FNAC.
Bethesda IV (follicular neoplasm): Diagnostic hemithyroidectomy — final diagnosis requires histological capsular/vascular invasion.
Pre-op for MTC: RET mutation, calcitonin, CEA, 24h urine metanephrines, Ca/PTH.
Iodinated contrast CT can interfere with subsequent RAI scan/therapy — plan accordingly.
TNM staging: Age < 55 with DTC → max Stage II. Anaplastic → auto Stage IV.
Active Recall - Diagnosis of Thyroid Cancer
References
[1] Senior notes: Ryan Ho Endocrine.pdf (Sections 1.6, 1.6.1, 1.6.2, pp. 19–20, 33–38) [2] Senior notes: felixlai.md (Thyroid cancer sections VIII–X, pp. 983–1014) [3] Senior notes: maxim.md (Thyroid cancer investigations, staging, approach to thyroid nodules) [5] Senior notes: Ryan Ho Fundamentals.pdf (pp. 426–428) [7] Lecture slides: GC 177. A thyroid nodule benign thyroid nodules; thyroid cancer.pdf (pp. 5, 7, 10, 13, 27) [8] Senior notes: Ryan Ho Diagnostic Radiology.pdf (p. 59 — thyroid scintigraphy) [9] Tessler FN, Middleton WD, Grant EG, et al. ACR Thyroid Imaging, Reporting and Data System (TI-RADS): White Paper of the ACR TI-RADS Committee. Journal of the American College of Radiology. 2017;14(5):587–595.
Management of Thyroid Cancer
The management of thyroid cancer is type-dependent and follows a logical sequence: (1) initial surgical treatment, (2) post-operative risk stratification, (3) adjuvant therapies, and (4) long-term surveillance. The beauty of thyroid cancer management lies in how the biology of the tumour dictates each treatment decision — well-differentiated cancers that retain iodine-avidity are exploited with radioiodine, while de-differentiated cancers that lose this property require alternative strategies.
Management considerations for well-differentiated thyroid carcinoma (WDTC) [4][7]:
- Extent of thyroidectomy: hemithyroidectomy vs total (bilateral) thyroidectomy
- Nature/aim and extent of lymph node/neck dissection: prophylactic or therapeutic; central and/or lateral compartments
- Postoperative adjuvant therapies: radioiodine (¹³¹I) ablation, external beam irradiation, thyroxine (T4) suppressive therapy
Before any thyroid surgery, there is a systematic pre-operative checklist:
| Pre-op Step | Rationale | Detail |
|---|---|---|
| Ensure biochemically euthyroid | Prevention of thyroid storm during surgery — a hyperthyroid patient undergoing neck manipulation risks intra-operative thyroid storm (massive release of T3/T4 from gland manipulation) [2][3] | Anti-thyroid drugs (carbimazole/propylthiouracil) until euthyroid; β-blockers for 2 weeks for symptom control |
| Vocal cord function by laryngoscopy | Mandatory pre-operative documentation of vocal cord function — medico-legal requirement. If a patient already has RLN palsy pre-operatively (from tumour invasion), this changes the surgical approach (must preserve the contralateral nerve at all costs to avoid bilateral palsy → airway obstruction) [1][3] | Direct or fibreoptic laryngoscopy |
| Calcium and vitamin D levels | Prevention of postoperative hypocalcaemia and hungry bone syndrome [2][3] | Monitor Ca²⁺ and vitamin D; supplement if low pre-operatively |
| Lugol's iodine solution (for Graves'/toxic) | Blocks iodine uptake and secretion of thyroid hormone; decreases vascularity of thyroid gland to reduce intraoperative bleeding [2] | Given 10 days prior to surgery. Wolff-Chaikoff effect: excess iodine paradoxically inhibits thyroid hormone synthesis |
| Imaging | Risk stratification and surgical planning | USG thyroid + neck LNs; ± CT/MRI if locally advanced; ± PET-CT for advanced disease [1] |
| Pre-op workup for MTC | Rule out phaeochromocytoma (catecholamine crisis risk under GA), assess familial disease | 24h urine metanephrines, Ca²⁺/PTH, calcitonin, CEA, RET mutation analysis [1][3] |
Critical Safety Point
NEVER take a patient with suspected MEN2-associated MTC to theatre without first ruling out phaeochromocytoma. If a phaeochromocytoma is present and undiagnosed, induction of anaesthesia or surgical manipulation can trigger a life-threatening catecholamine crisis with malignant hypertension, arrhythmias, and cardiovascular collapse. Always check 24h urine metanephrines/plasma metanephrines first.
12.4 Surgical Management
| Term | Definition |
|---|---|
| Total thyroidectomy | Resection of both lobes + isthmus + pyramidal lobe [3] |
| Subtotal thyroidectomy | Resection of > 1/2 of both lobes + isthmus [3] (rarely done for cancer) |
| Hemithyroidectomy | Resection of one lobe + isthmus [3] |
| Lobectomy | Resection of one lobe (isthmus preserved) [3] |
| Near-total thyroidectomy | Removal of virtually all thyroid tissue except a small remnant ( < 1 g) near the RLN on one side |
| Completion thyroidectomy | Removal of the remaining lobe after initial hemithyroidectomy, when final histopathology reveals cancer requiring total thyroidectomy |
Alternative surgical approaches (for cosmesis) [3]:
- Bilateral axillo-breast approach (BABA)
- Transoral vestibular approach
- Retro-auricular trans-hairline approach (RATH)
General indications for thyroidectomy (the "4 C's") [3]:
- CA thyroid
- Uncontrolled thyrotoxicosis (Cannot be treated medically)
- Compression symptoms
- Cosmetic concern
B. Surgical Approach by Cancer Type
This is the most nuanced decision-making area — the choice between hemithyroidectomy and total thyroidectomy depends on tumour size, risk features, and patient/team preference.
Hemithyroidectomy (Lobectomy + Isthmusectomy):
| Indication | Rationale |
|---|---|
| Microcarcinoma (tumour < 1 cm) WITHOUT extrathyroidal extension or vascular invasion [2][7] | Excellent prognosis; completion thyroidectomy can be done later if higher-risk features found on final histology |
| Tumour 1–4 cm WITHOUT extrathyroidal extension or vascular invasion, N0 [2][4][7][9] | ATA 2015: "Thyroid lobectomy alone may be sufficient initial treatment for low-risk papillary and follicular carcinomas" |
| Bethesda IV (follicular neoplasm) — diagnostic | To obtain histological diagnosis; completion TT if cancer confirmed on final pathology |
Arguments for hemithyroidectomy [7]:
- Lower morbidity (avoids bilateral RLN risk, lower hypoparathyroidism risk)
- Avoid lifelong T4 replacement (remaining lobe maintains thyroid function in ~80% of patients)
Total Thyroidectomy (or Near-Total Thyroidectomy):
| Indication | Rationale |
|---|---|
| Tumour > 4 cm [2][4][9] | Large tumours carry higher recurrence risk; need RAI ablation post-op |
| Tumour with extrathyroidal extension (ETE) [2][4][9] | Aggressive feature indicating higher stage disease |
| Tumour with lymph node metastasis (N1) or distant metastasis (M1) [2][4][9] | Need RAI for adjuvant treatment; need Tg monitoring |
| Aggressive histology (tall cell, columnar cell, diffuse sclerosing, poorly differentiated PTC, Hürthle cell) [3] | Higher recurrence risk |
| Bilateral or multifocal disease [7] | Papillary CA is commonly multifocal (70%) and bilateral |
| Patient/team preference when RAI ablation or Tg monitoring desired [7][9] | Total thyroidectomy enables RAI and makes Tg a reliable tumour marker |
Arguments for total thyroidectomy [7]:
- Commonly multifocal and bilateral → addresses occult contralateral disease
- Excellent survival and low recurrence
- Allows RAI ablation and thyroglobulin (Tg) monitoring
- Low morbidity rate by experienced surgeons
The Controversy for Low-Risk PTC
For early-stage PTC ( < 4 cm, no invasion, no LN metastasis), there is genuine management controversy [7]. Survival is nearly 100% regardless of whether hemithyroidectomy or total thyroidectomy is performed. The debate centres on overtreatment/surgical risk vs avoiding recurrence/facilitating follow-up. Patients' vs physicians' preference matters, and this is moving towards personalised treatment [7]. Active surveillance (watchful waiting) is now an accepted option for papillary microcarcinomas ( < 1 cm) in selected patients — pioneered by Japanese centres (Kuma Hospital, Miyauchi protocol).
ATA 2015 Guideline Statement [9]:
"For patients with thyroid cancer > 1 cm and < 4 cm without extrathyroidal extension, and without clinical evidence of any lymph node metastases (cN0), the initial surgical procedure can be either a bilateral procedure (near-total or total thyroidectomy) or a unilateral procedure (lobectomy). Thyroid lobectomy alone may be sufficient initial treatment for low-risk papillary and follicular carcinomas; however, the treatment team may choose total thyroidectomy to enable RAI therapy or to enhance follow-up based upon disease features and/or patient preferences." — Strong recommendation, moderate-quality evidence
- FTC is usually diagnosed post-operatively (because FNAC cannot distinguish follicular adenoma from carcinoma — Bethesda IV).
- Initial surgery is typically diagnostic hemithyroidectomy. The decision to perform completion thyroidectomy is based on the final histopathology:
- Hemithyroidectomy post-op: thyroxine replacement is NOT required immediately — measure TSH 6 weeks later [2]
| Management Step | Detail | Rationale |
|---|---|---|
| Total thyroidectomy | ALL medullary carcinoma should undergo total thyroidectomy [1][2][7] | Aggressive nature; majority already locally advanced or metastatic at diagnosis; risk of multifocality and bilaterality; association with MEN [2] |
| Central compartment dissection (Level VI) | Prophylactic dissection indicated in ALL cases whether or not there is evidence of LN involvement [2][7] | MTC has early nodal metastasis; Level VI is the first echelon |
| Lateral neck dissection | Prophylactic if central compartment is involved; therapeutic if lateral nodes confirmed [2][3] | Depends on calcitonin level and imaging: ipsilateral LCD if calcitonin < 200; bilateral LCD if calcitonin > 200 [3] |
| Genetic analysis: RET proto-oncogene | Test all MTC patients [1][7] | 25% are familial (MEN2A/2B/FMTC) |
| Prophylactic thyroidectomy in RET carriers | Best done at age 5–10 years [1][7] | Virtually 100% penetrance for MTC in MEN2 |
| Aim: biochemical cure | Normalised calcitonin post-operatively [1] | Rising calcitonin post-op → screen for residual/metastatic disease |
| Post-op T4 replacement | Keep euthyroid — NOT TSH suppression (unlike DTC) [1] | MTC arises from C cells which do NOT express TSH receptors → TSH suppression has no anti-tumour effect |
| No good adjuvant treatment | No role for RAI (C cells don't take up iodine) [1] | C cells lack NIS expression |
| Follow-up | Serum calcitonin and CEA 6 months post-op [1]; ↑calcitonin → screen for residual/metastatic disease → surgical Tx ± chemo/RT [1] |
Why doesn't MTC respond to RAI? MTC arises from parafollicular C cells, not follicular epithelial cells. C cells do not express the sodium-iodide symporter (NIS) and do not organify iodine — they have a completely different embryological origin (neural crest) and function (calcitonin secretion). Therefore, radioiodine cannot be concentrated in medullary carcinoma cells.
| Management | Detail |
|---|---|
| Automatically Stage IV | All anaplastic CA is Stage IV at diagnosis regardless of extent [1][3] |
| Total thyroidectomy with post-operative chemoradiotherapy | Indicated in patients with intrathyroidal anaplastic carcinoma or locally advanced disease. Post-operative combined chemotherapy and radiotherapy prolong survival [2] |
| Chemoirradiation ± surgical debulking | For surgically inoperable disease [1][2][7] |
| Palliative tracheostomy | Death is usually attributable to upper airway obstruction and suffocation; tracheostomy is indicated to secure the airway [2] |
| Targeted therapy | Chemoirradiation + resection + targeted Rx [7]. Dabrafenib + trametinib for BRAF V600E-mutant anaplastic CA (FDA approved 2018, landmark ROAR basket trial); lenvatinib; immunotherapy (pembrolizumab if PD-L1+/MSI-H) |
| Prognosis | Median survival < 6 months. Lack of effective treatment. Invariably palliative and fatal [1][7] |
Understanding lymph node dissection terminology and indications is critical:
Terminology:
| Type | Extent |
|---|---|
| Central compartment dissection (CCD) | Level VI (± Level VII) — pretracheal, paratracheal, prelaryngeal nodes |
| Lateral neck dissection (LCD) | Level II–V nodes |
| Radical neck dissection (RND) | Removal of all ipsilateral lymphatic structures + IJV + SCM + CN XI (rarely done now) [1] |
| Modified radical neck dissection (MRND) | 1–3 of IJV, SCM, CN XI preserved [1] |
| Functional neck dissection | All 3 of IJV, SCM, CN XI preserved [1] |
| Selective neck dissection | Only selected levels dissected |
Indications by Cancer Type:
| Cancer | Central Compartment (Level VI) | Lateral Compartment (Levels II–V) |
|---|---|---|
| Papillary CA | Therapeutic CCD if confirmed involved; Prophylactic CCD controversial — only for advanced disease (T3–T4) or lateral LN involvement [1][2][3] | Therapeutic LCD if confirmed involved; NO prophylactic lateral dissection [2][3] |
| Follicular CA | Usually not required (haematogenous spread; LN metastasis uncommon at 8–13%) [3] | Rare |
| Medullary CA | Prophylactic CCD for ALL patients [2][3][7] | Prophylactic LCD if central compartment involved; therapeutic if lateral nodes confirmed [2][3] |
| Anaplastic CA | If resectable — but usually palliative | If resectable |
Central LN metastasis is present in 50% of papillary thyroid carcinoma cases [1]. However, prophylactic central dissection is NOT routinely recommended unless there is advanced disease (T3–T4) or lateral LN involvement, because: (1) most micro-metastases may not be clinically significant, (2) increased risk of hypoparathyroidism and RLN injury with bilateral central dissection [1].
12.5 Post-operative Management
| Step | Detail |
|---|---|
| Histopathology | Determines final T, N staging; identifies aggressive features (ETE, vascular invasion, histological subtype) |
| Thyroglobulin | Post-op baseline: < 5 ng/mL after total thyroidectomy; < 30 ng/mL after hemithyroidectomy [1][3] |
| TNM staging | Predicts disease-specific mortality |
| ATA risk stratification | Predicts risk of recurrence → guides intensity of adjuvant therapy [1][9] |
T4 therapy post-thyroidectomy serves a dual role [2][3]:
- Replacement — prevent hypothyroidism (mandatory after total thyroidectomy)
- Suppression — suppress TSH to reduce stimulation of any residual DTC cells (because differentiated thyroid carcinoma expresses TSH receptors → TSH is a growth factor)
Target TSH depends on risk — note that the low-risk group does NOT require TSH suppression [3]:
| ATA Risk | Features | Target TSH |
|---|---|---|
| Low risk | None of the high/intermediate features | No TSH suppression: 0.5–2.0 mIU/L [3] |
| Intermediate risk | T3, N1, aggressive histology, vascular invasion | Low TSH suppression: 0.1–0.5 mIU/L [3] |
| High risk | T4, M1, incomplete resection | High TSH suppression: < 0.1 mIU/L [1][3][9] |
After hemithyroidectomy [2]:
- Do NOT start T4 therapy immediately post-operatively
- Measure serum TSH 6 weeks after surgery and determine need for T4 based on TSH and evaluation of post-operative disease status
After total thyroidectomy [2]:
- If NO RAI ablation needed → start T4 immediately post-operatively
- If RAI ablation required AND patient CAN tolerate prolonged hypothyroidism → withhold T4 for ≥ 4 weeks (or T3 for ≥ 2 weeks) before RAI to allow TSH to rise
- If RAI ablation required AND patient CANNOT tolerate prolonged hypothyroidism (e.g. cardiovascular disease) → start T3 therapy (shorter half-life, ~1 day vs T4 ~7 days) and stop 2 weeks prior to RAI, OR use recombinant human TSH (rhTSH, Thyrogen®) injection [2]
Precautions of long-term TSH suppression [2]:
- Osteoporosis → calcium supplements required (chronic subclinical hyperthyroidism accelerates bone resorption)
- Atrial fibrillation and cardiac dysfunction → may need to relax TSH target in elderly or those with cardiac disease
For MTC: T4 replacement to keep euthyroid only — NOT TSH suppression (C cells lack TSH receptors) [1]
This is one of the most important adjuvant therapies and a frequently examined topic.
Rationale [2]:
- Ablate remaining normal thyroid tissue (remnant ablation) — eliminates the source of background Tg, making Tg a more sensitive recurrence marker
- Treatment of clinically apparent residual thyroid cancer (residual tumour ablation)
- Treatment of subclinical micrometastasis
- Treatment of metastatic thyroid cancer
Why does residual thyroid tissue interfere with Tg monitoring? Normal thyroid remnant produces thyroglobulin, creating a "background noise" that obscures detection of tumour-derived Tg. By ablating all residual normal thyroid with RAI, any subsequently detectable Tg must come from residual or recurrent cancer [3].
Mechanism: ¹³¹I is taken up by thyroid cells via the sodium-iodide symporter (NIS), just like normal iodine. Once intracellular, ¹³¹I emits β particles (primary therapeutic effect — short range, ~0.5 mm tissue penetration → destroys neighbouring cells) and γ rays (used for imaging/scanning). The β radiation causes DNA damage → cell death in follicular cells that have concentrated the isotope [1].
Indications for RAI Ablation After Total Thyroidectomy [2][3][9]:
| Risk | RAI Recommended? | Description |
|---|---|---|
| Low | Not recommended | Unifocal cancer < 1 cm without high-risk features; Multifocal cancer when all foci < 1 cm without high-risk features [2] |
| Intermediate | Selectively considered | Intrathyroidal cancer 1–4 cm without high-risk features; Vascular invasion; Microscopic invasion into perithyroidal soft tissues; Clinically significant LN metastasis outside thyroid bed; Aggressive histological subtypes (tall cell variant PTC, Hürthle cell variant FTC) [2] |
| High | Recommended | Macroscopic tumour invasion; Incomplete tumour resection with gross residual disease; Distant metastasis [2] |
Indications similar to those for total thyroidectomy [3]:
- T3/T4 disease
- N1/M1 disease
- Aggressive histology: tall cell, columnar cell, diffuse sclerosing, poorly differentiated PTC
Preparation Before RAI [2][3]:
- Low iodine diet for ≥ 1–2 weeks — depletes intrathyroidal iodine stores, maximising subsequent ¹³¹I uptake
- Withdrawal of T4 for ≥ 4 weeks (or T3 for ≥ 2 weeks) — allows TSH to rise ( > 30 mIU/L target), which stimulates NIS expression and promotes RAI uptake by residual tumour [2]
- Recombinant human TSH (rhTSH/Thyrogen®) injection — alternative for patients who cannot tolerate prolonged hypothyroidism (e.g. CVS disease). Achieves TSH stimulation without thyroid hormone withdrawal [2]
After RAI Ablation [2]:
- Avoid pregnancy for 1 year until disease becomes stable (radiation effect on gametes)
- Post-therapy RAI whole-body scan — 1 week after ablation → screen for RAI uptake of residual tumour and screen for distant metastasis
- Start TSH suppression therapy — supra-physiological dose of T4 to suppress TSH to target level based on risk
- 2nd post-RAI whole-body scan at 6–12 months → screen for tumour recurrence and distant metastasis [2]
Contraindications to RAI:
- Pregnancy and breastfeeding (¹³¹I crosses the placenta and is concentrated in fetal thyroid after 12 weeks; secreted in breast milk)
- Medullary thyroid carcinoma (C cells lack NIS — no iodine uptake)
- Anaplastic carcinoma (de-differentiated, lost NIS expression)
- Recent iodinated contrast administration (4–8 week washout needed)
| Indication | Rationale |
|---|---|
| Positive surgical margins / incomplete resection (R2 — macroscopic residual disease) [1][3][9] | RAI may not be sufficient for gross residual disease; EBRT provides local control |
| Inoperable residual disease | Cannot be surgically excised |
| Anaplastic carcinoma (as part of chemoirradiation) | Palliative; may prolong survival modestly |
| MTC with residual disease | No RAI option; EBRT considered for local control |
Management of high-risk patients includes [9]:
- Total or near-total thyroidectomy
- Central compartment neck dissection
- (± Compartmental neck dissection)
- Radioiodine ablation
- External beam irradiation for incomplete resection (R2)
- Thyroxine suppression therapy (TSH < 0.03)
For radioiodine-refractory differentiated thyroid cancer (i.e. tumours that have lost NIS expression and no longer take up iodine), or advanced/metastatic MTC:
| Agent | Type | Indication | Notes |
|---|---|---|---|
| Lenvatinib | Multi-kinase inhibitor (VEGFR, FGFR, RET, KIT, PDGFRα) | RAI-refractory DTC | SELECT trial — improved PFS. First-line for progressive, RAI-refractory DTC |
| Sorafenib | Multi-kinase inhibitor (VEGFR, RAF, RET) | RAI-refractory DTC | DECISION trial — improved PFS |
| Vandetanib | Multi-kinase inhibitor (VEGFR, EGFR, RET) | Advanced MTC | ZETA trial |
| Cabozantinib | Multi-kinase inhibitor (MET, VEGFR2, RET) | Advanced MTC | EXAM trial |
| Selpercatinib / Pralsetinib | Highly selective RET inhibitors | RET-mutant MTC; RET fusion-positive DTC | LIBRETTO-001 / ARROW trials; excellent response rates with fewer off-target effects |
| Dabrafenib + Trametinib | BRAF + MEK inhibitors | BRAF V600E-mutant anaplastic thyroid carcinoma | FDA approved 2018 based on ROAR trial — first approved combination for anaplastic CA; this is a game-changer for a previously uniformly fatal disease |
| Pembrolizumab | Anti-PD-1 immune checkpoint inhibitor | PD-L1+ or MSI-H thyroid cancers | Emerging role in anaplastic CA |
Why are multi-kinase inhibitors effective in thyroid cancer? Thyroid cancers are driven by the RET-RAS-BRAF-MAPK pathway. Multi-kinase inhibitors block these oncogenic drivers AND the VEGF pathway (anti-angiogenesis). The result is both direct anti-tumour activity and starvation of the tumour blood supply.
| Modality | Timing | Target/Interpretation |
|---|---|---|
| Neck USG | Every 6 months [3] | Assess thyroid bed (or remaining lobe) and cervical lymph nodes for recurrence |
| TSH level | Every 3–6 months [3] | Ensure TSH is at target suppression level |
| Serum thyroglobulin (Tg) | Every 3–6 months (on thyroxine suppression) [3] | Total thyroidectomy: Tg < 0.2 ng/mL; Hemithyroidectomy: Tg < 30 ng/mL [3]. Rising Tg = recurrence |
| Anti-TG antibodies | With each Tg measurement | If positive, Tg is unreliable → follow anti-TG antibody trend as surrogate |
| RAI whole-body scan | 6–12 months post-RAI ablation (then as needed) | Screen for recurrence, distant metastasis [2] |
| Calcitonin + CEA (for MTC) | 6 months post-op, then periodically [1] | Rising calcitonin → screen for residual/metastatic disease [1] |
| Stimulated Tg test | 9–12 months post-treatment | Tg measured after TSH stimulation (rhTSH or T4 withdrawal) — higher sensitivity for detecting residual disease |
| FDG PET-CT | When Tg rising but RAI scan negative | "Flip-flop" phenomenon: de-differentiated tumours lose iodine avidity but gain FDG avidity |
| Feature | Papillary CA | Follicular CA | Medullary CA | Anaplastic CA | Lymphoma |
|---|---|---|---|---|---|
| Surgery | HemiT or TT (based on risk) | Diagnostic HemiT → completion TT if widely invasive | TT for ALL | TT + debulking if possible | Not primary surgery |
| LN dissection | Therapeutic CCD/LCD; prophylactic CCD for T3–4 | Usually not required | Prophylactic CCD for ALL; LCD based on calcitonin | If resectable | Not applicable |
| RAI | Based on risk (low = No, intermediate = consider, high = Yes) | Based on risk | NO (C cells lack NIS) | NO (lost NIS) | No |
| EBRT | For R2 residual | For R2 residual | For residual disease | Part of chemoirradiation | Part of standard Rx |
| T4 therapy | Replacement ± suppression (risk-based TSH target) | Same | Replacement only (euthyroid target) | If post-TT | N/A |
| Chemo/targeted | Lenvatinib/sorafenib if RAI-refractory | Same | Vandetanib/cabozantinib/selpercatinib | Dabrafenib+trametinib if BRAF+; chemo | R-CHOP |
| Tumour marker | Tg | Tg | Calcitonin, CEA | None reliable | None specific |
| Prognosis | Excellent | Good | Moderate (5y 60–70%) | Dismal ( < 6 months) | Median 9 years |
High Yield Summary
Surgical decision: HemiT for low-risk DTC ( < 4 cm, no ETE, N0); TT for high-risk DTC ( > 4 cm, ETE, N1, M1, aggressive histology); TT for ALL MTC; palliative for anaplastic.
LN dissection: Papillary — therapeutic CCD/LCD, prophylactic CCD only for advanced disease. MTC — prophylactic CCD for ALL. Follicular — usually not required.
Pre-op essentials: Euthyroid status, laryngoscopy (vocal cords), Ca/VitD, rule out phaeo in MTC.
T4 post-op: Dual role (replacement + TSH suppression). Low risk: TSH 0.5–2.0; Intermediate: 0.1–0.5; High: < 0.1. MTC: euthyroid only, no suppression.
RAI: Exploits NIS expression in DTC. Not for MTC or anaplastic. Preparation: low-iodine diet, T4 withdrawal (or rhTSH), avoid pregnancy 1 year post-RAI. Low-risk DTC does NOT need RAI.
EBRT: For R2 (macroscopic residual), incomplete resection, anaplastic CA.
Targeted therapy: Lenvatinib/sorafenib for RAI-refractory DTC; selpercatinib/vandetanib/cabozantinib for MTC; dabrafenib+trametinib for BRAF V600E anaplastic CA.
Surveillance: USG Q6m, Tg Q3–6m, calcitonin/CEA for MTC, RAI WBS at 6–12m post-RAI.
Active Recall - Management of Thyroid Cancer
References
[1] Senior notes: Ryan Ho Endocrine.pdf (Sections 1.6, 1.6.1, 1.6.2, pp. 21, 25, 33–38, 132) [2] Senior notes: felixlai.md (Thyroid cancer sections IX–X, pp. 1007–1014) [3] Senior notes: maxim.md (Thyroid cancer management, thyroidectomy, post-op adjuvant, thyroxine, surveillance) [4] Lecture slides: Management of differentiated thyroid carcinoma.pdf (pp. 8, 9, 11, 16) [5] Senior notes: Ryan Ho Fundamentals.pdf (pp. 427–428) [7] Lecture slides: GC 177. A thyroid nodule benign thyroid nodules; thyroid cancer.pdf (pp. 20, 22, 27, 28) [9] Lecture slides: Management of differentiated thyroid carcinoma.pdf (p. 9 — ATA 2015 guideline statement; p. 11 — ATA risk stratification; p. 16 — high-risk management)
Complications of Thyroid Cancer and Its Treatment
Complications in thyroid cancer can be divided into two broad categories: (1) complications of the disease itself (from tumour growth, invasion, and metastasis), and (2) complications of treatment (primarily surgical complications of thyroidectomy and side effects of RAI/T4 therapy). In clinical practice and exams, surgical complications of thyroidectomy are by far the most frequently tested — so we will cover these in exhaustive detail.
13.1 Complications of the Disease Itself
These arise from the biological behaviour of the tumour — local invasion, regional spread, and distant metastasis.
| Complication | Mechanism | Clinical Features |
|---|---|---|
| Recurrent laryngeal nerve (RLN) invasion | Tumour directly invades the RLN in the tracheo-oesophageal groove → interrupts motor supply to all intrinsic laryngeal muscles except cricothyroid | Unilateral: hoarseness, breathy voice, ineffective cough, aspiration risk. Bilateral: stridor, dyspnoea, airway obstruction (because 6 adductor muscles overpower 2 abductors → cords close) [2][3] |
| Tracheal invasion/compression | Direct tumour extension into or compression of the trachea | Dyspnoea, stridor, haemoptysis. May require palliative tracheostomy (especially in anaplastic CA where death is usually attributable to upper airway obstruction) [1][2] |
| Oesophageal invasion/compression | Direct tumour extension posteriorly into the oesophagus | Dysphagia (difficulty swallowing), odynophagia |
| Carotid artery/jugular vein encasement | Advanced T4b disease — tumour encases major vessels | Horner's syndrome (sympathetic chain), cerebrovascular ischaemia (rare) |
| Superior vena cava obstruction (SVCO) | Large retrosternal goitre or tumour compressing thoracic inlet structures | Facial plethora, distended neck veins, arm oedema, Pemberton's sign positive |
| Cervical lymphadenopathy | Lymphatic metastasis (especially papillary CA → Level VI first echelon) | Palpable, firm, non-tender neck masses. Can be the presenting complaint, especially in young patients with small primary tumours [1] |
Why is airway obstruction the usual cause of death in anaplastic CA? Anaplastic carcinoma grows explosively — doubling time is measured in days to weeks rather than months. The tumour rapidly infiltrates the trachea and surrounding structures, causing progressive airway compromise. Because the tumour is de-differentiated, it does not respond to RAI, and the patients are typically elderly with poor comorbid states, leaving very limited therapeutic options [1][2].
| Site | Cancer Type | Mechanism | Clinical Features |
|---|---|---|---|
| Lungs | PTC > FTC | Haematogenous (FTC) or lymphatic then haematogenous (PTC) | Cough, haemoptysis, dyspnoea, cannonball lesions (FTC) or miliary pattern (PTC) on CXR |
| Bone | FTC > PTC | Haematogenous; lytic lesions (FTC has particular predilection for bone) | Bone pain, pathological fractures, hypercalcaemia of malignancy, spinal cord compression |
| Liver | FTC, MTC | Haematogenous | Hepatomegaly, deranged LFTs, jaundice (rare) |
| Brain | FTC (rare) | Haematogenous | Headache, seizures, focal neurological deficits |
| Complication | Cancer Type | Mechanism |
|---|---|---|
| Secretory diarrhoea and flushing | MTC | Calcitonin and other peptides (prostaglandins, serotonin, VIP) produced by C-cell tumour → stimulate intestinal secretion |
| Hypercalcaemia | Advanced metastatic disease; MEN2A (concurrent parathyroid hyperplasia) | Bone metastases → local osteolysis → calcium release; or concurrent primary hyperparathyroidism in MEN2A |
| Cushing syndrome | MTC (rare) | Ectopic ACTH production by the neuroendocrine tumour |
13.2 Complications of Treatment — Thyroidectomy
This is the most examinable section. Thyroidectomy complications are classified by timing:
| Complication | Mechanism | Clinical Features | Management |
|---|---|---|---|
| Intraoperative haemorrhage | Injury to superior/inferior thyroid arteries, thyroid veins, or other vascular structures during dissection | Bleeding in the operative field; haemodynamic instability if significant | Immediate haemostasis; ligate/cauterise bleeding vessel |
| Oesophageal injury | Direct surgical trauma to the posterior oesophageal wall during dissection of a posteriorly located tumour or Berry's ligament | Saliva/food leak, mediastinitis (if unrecognised) | Primary repair if identified intra-operatively; high morbidity if missed |
| Tracheal injury | Inadvertent surgical trauma, especially with tumour adherent to trachea | Air leak, subcutaneous emphysema | Primary repair |
| Tracheomalacia | Degeneration of tracheal cartilage following removal of chronic compression by a large goitre → tracheal wall becomes floppy and collapses during inspiration | Stridor and respiratory distress upon extubation (the "floppy trachea") | Positive pressure ventilation initially; may require tracheostomy or tracheal stenting in severe cases |
| Thyroid storm | Develops in patients with longstanding untreated hyperthyroidism precipitated by acute event such as surgery → rapid increase in serum thyroid hormone levels → increased response to sympathetic inputs from catecholamines by permissive effect [2] | Hyperpyrexia (fever > 39°C), tachycardia, hypertension → progressing to heart failure with hypotension and arrhythmia, agitation, delirium [2] | Lugol's iodine, β-blockers, PTU (blocks T4→T3 conversion), hydrocortisone, cooling measures, supportive ICU care |
| Superior laryngeal nerve (SLN) injury (external branch) | SLN supplies the cricothyroid muscle which lengthens (tenses) the vocal cord to produce high-pitched sound [2]. Injury occurs during ligation of the superior thyroid artery near the superior pole | Vocal fatigue and changes in voice quality; inability to sing high-pitched notes; reduced vocal projection [2][1] | Usually permanent; voice therapy. Important to ask pre-operatively if the patient is a professional singer [1] |
| Recurrent laryngeal nerve (RLN) injury | Surgical trauma (transection, thermal injury, traction neuropraxia) to the RLN in the tracheo-oesophageal groove. RLN supplies all intrinsic muscles of the larynx except cricothyroid [2] | See detailed box below | See detailed box below |
RLN Injury — In-Depth (The Most Feared Complication)
This complication occurs in < 1% of thyroidectomies performed by experienced surgeons [1], but its consequences are devastating. Understanding the anatomy explains the clinical features:
- The RLN innervates all intrinsic laryngeal muscles except the cricothyroid — this includes both the abductors (posterior cricoarytenoid — the ONLY abductor, which opens the glottis) and the adductors (lateral cricoarytenoid, thyroarytenoid, interarytenoid, which close the glottis).
- There are 6 adductor muscles vs only 2 abductor muscles (one posterior cricoarytenoid on each side). This numerical imbalance is critical for understanding bilateral injury.
| Scenario | Pathology | Clinical Features | Why? |
|---|---|---|---|
| Unilateral RLN injury | Ipsilateral vocal cord paralysis — cord fixed in paramedian position | Hoarseness, breathy voice, ineffective cough, increased risk of aspiration pneumonia [2] | The paralysed cord cannot adduct or abduct → air escapes through the gap during phonation (hoarseness); poor glottic closure during swallowing (aspiration) |
| Bilateral RLN injury | Both vocal cords paralysed — cords fixed in adducted (midline) position | Stridor, dyspnoea, acute airway obstruction [2][3] | Because there are 6 adductors vs only 2 abductors, in bilateral injury the cords default to the midline (adducted) position → the glottis is nearly closed → critical airway compromise [3] |
- Transient vs permanent: Injury can be transient (tractional neuropraxia) — nerve stretched but not transected, recovers in weeks to months — or permanent (transection or thermal damage) [1].
- Management of unilateral RLN injury: Cord medialization procedures — injection thyroplasty (inject fat/filler into paralysed cord to push it medially for better apposition with the functioning cord) or open medialization thyroplasty (e.g. Gore-Tex implant) [3].
- Management of bilateral RLN injury: This is an emergency — patient develops stridor and dyspnoea upon extubation → immediate re-intubation ± tracheostomy [1][3].
Exam Must-Know
Bilateral RLN injury causes airway obstruction (stridor, dyspnoea), NOT just voice changes. This is because 6 adductor muscles overpower 2 abductors, so both cords default to the adducted (closed) position. The voice may actually sound relatively normal (cords are apposed) but the patient cannot breathe. This is a surgical emergency requiring immediate re-intubation or tracheostomy.
| Complication | Mechanism | Clinical Features | Management |
|---|---|---|---|
| Post-operative haematoma (1.25%) | Reactionary or secondary haemorrhage into the surgical bed, usually in the paratracheal region below the strap muscles | Large, tense, firm, immobile neck swelling + SOB [1]. Significance: causes venous obstruction → acute laryngeal oedema → risk of airway compromise [1] | EMERGENCY: Cut subcuticular stitches and stitches holding strap muscles at the bedside to evacuate blood → call seniors for intubation/theatre [1]. This is a bedside procedure — do NOT wait for theatre. Every second counts |
| Seroma | Accumulation of serous fluid in the surgical dead space | Superficial, mobile swelling (much softer and more mobile than haematoma) | Usually self-limiting; aspirate if large or symptomatic [1] |
| Wound infection | Bacterial contamination of the surgical wound | Erythema, warmth, purulent discharge, fever | Antibiotics, wound care. Note: wound infection is rare because thyroidectomy is a clean surgical field [3] |
| Hyperthyroidism ± thyroid storm | Release of stored thyroid hormone into the bloodstream during surgical manipulation [1] | Same as thyroid storm above — managed with β-blockers, anti-thyroid drugs, supportive care | Prevention is key: ensure patient is euthyroid pre-operatively |
| Dysphagia | Unclear mechanism — possibly related to surgical trauma to perithyroidal tissues, strap muscle dissection, or oedema | Difficulty swallowing (usually mild) | Usually resolves spontaneously [1] |
How to Manage a Post-Thyroidectomy Neck Haematoma — Step by Step
This is a classic emergency station scenario. The expanding haematoma compresses the airway from outside via venous congestion → laryngeal oedema. You have minutes, not hours.
- Recognise: patient is dyspnoeic, has a tense, expanding neck swelling within hours of thyroidectomy.
- Call for help: alert the senior surgeon and anaesthetist.
- Open the wound at the bedside: remove skin clips/subcuticular sutures and deep strap muscle sutures. Allow blood to drain. This immediately decompresses the airway.
- Secure the airway: prepare for intubation (difficult airway anticipated due to oedema) or surgical airway if cannot intubate.
- Return to theatre: for formal exploration, haemostasis, and wound closure under controlled conditions.
| Complication | Mechanism | Clinical Features | Management |
|---|---|---|---|
| Hypoparathyroidism leading to hypocalcaemia | MOST common complication of thyroidectomy [2][3]. Caused by inadvertent removal, devascularisation, or surgical trauma to the parathyroid glands (4 glands embedded in or near the thyroid). Only in total/subtotal thyroidectomy (hemithyroidectomy spares the contralateral parathyroids) [3]. Risk: 1–4% permanent (especially in cancer surgery as extensive dissection is required), 10–20% transient (especially in ischaemia) [1] | See detailed box below | See detailed box below |
| Hungry bone syndrome (HBS) | Severe and prolonged hypocalcaemia despite normal or even elevated levels of PTH [2]. Sudden removal of the effect of high circulating thyroid hormones (or PTH in MEN2A) → increased influx of calcium into bones (remineralisation of chronically demineralised bone) | Profound hypocalcaemia + hypophosphataemia + hypomagnesaemia [2]. Occurs particularly in patients with pre-operative hyperthyroidism (high bone turnover state) [1] | Aggressive IV calcium + calcitriol replacement; IV magnesium if low |
| Hypothyroidism | Loss of thyroid tissue → insufficient T4 production | Fatigue, weight gain, cold intolerance, constipation, bradycardia | Levothyroxine replacement (lifelong after total thyroidectomy; ~5% need it after hemithyroidectomy [1]) |
| Tumour recurrence | Residual microscopic disease; inadequate initial surgery; aggressive tumour biology | Rising thyroglobulin (DTC) or calcitonin (MTC); palpable neck mass; new lymphadenopathy on USG | Depends on extent: completion surgery, RAI, targeted therapy |
| Hypertrophic scar / keloid formation | Abnormal wound healing with excessive collagen deposition | Raised, thickened scar across the anterior neck | Silicone sheets, intralesional corticosteroid injection, pressure garments |
Hypoparathyroidism and Hypocalcaemia — In-Depth
This is the most common complication and the one you must know cold:
Why does it happen? The four parathyroid glands sit directly on the posterior surface of the thyroid. During thyroidectomy, they can be:
- Inadvertently excised (removed with the thyroid specimen)
- Devascularised — often due to compromise of the inferior thyroid artery (which supplies all four parathyroids) [1]
- Damaged by thermal injury from electrocautery
Time course:
- Transient hypoparathyroidism (10–20%): parathyroid glands are stunned/ischaemic but recover over days to weeks
- Permanent hypoparathyroidism (1–4%): glands destroyed or removed → lifelong calcium and vitamin D supplementation
Clinical features of hypocalcaemia — Mnemonic: "CATS GO NUMB" [1]:
- Convulsions
- Arrhythmias (prolonged QT interval on ECG)
- Tetany
- Spasm of the larynx (laryngospasm — this can cause acute airway obstruction requiring emergency intubation/surgical airway [3])
- GO: —
- NUMBness — perioral and acral (fingertip) paraesthesia [2][3] (earliest symptom — always ask about tingling around the mouth and fingertips)
Signs to elicit:
- Chvostek's sign — tapping over the facial nerve (anterior to the ear, below the zygomatic arch) causes ipsilateral facial muscle twitching. This occurs because hypocalcaemia lowers the threshold for nerve depolarisation → increased neuromuscular excitability.
- Trousseau's sign — inflating a blood pressure cuff above systolic pressure for 3 minutes causes carpopedal spasm (main d'accoucheur — wrist flexion, metacarpophalangeal flexion, interphalangeal extension, thumb adduction). More specific than Chvostek's sign.
Investigation:
- Serum corrected calcium (Ca²⁺) or ionised calcium — check routinely post-operatively (day 1) [1][3]
- Serum PTH level — distinguishes hypoparathyroidism (low PTH) from hungry bone syndrome (normal/elevated PTH)
- ECG — prolonged QT interval ± arrhythmia [1]
- Acute/severe symptomatic hypocalcaemia: IV 10–20 mL of 10% calcium gluconate over 10 minutes (slow bolus) [2]. Can repeat or start IV calcium infusion.
- Maintenance replacement: Oral calcium carbonate + calcitriol (active vitamin D, 1,25-dihydroxycholecalciferol) [2][3]. Calcitriol is used instead of cholecalciferol because the kidneys require PTH to convert 25-hydroxyvitamin D to the active 1,25-form — without PTH, this conversion is impaired.
Why calcitriol specifically? In hypoparathyroidism, the enzyme 1α-hydroxylase in the kidney (which converts 25-OH vitamin D to its active form, 1,25-dihydroxycholecalciferol) is not stimulated because PTH is absent. Therefore, giving regular vitamin D (cholecalciferol) is ineffective — you must give the already-activated form (calcitriol) to bypass this enzymatic block.
| Complication | Mechanism | Detail |
|---|---|---|
| Radiation sialadenitis/xerostomia | ¹³¹I is concentrated by salivary glands (they also express NIS) → radiation damage to acinar cells | Painful swelling of parotid/submandibular glands; chronic dry mouth (xerostomia). Managed with sour candy/lemon juice (stimulate salivary flow), hydration |
| Transient thyroiditis | Radiation-induced inflammation of residual thyroid tissue | Anterior neck pain, transient thyrotoxicosis (release of stored hormone from damaged cells) |
| Nausea/vomiting | Gastrointestinal radiation effect (¹³¹I in gastric mucosa) | Usually self-limiting; anti-emetics |
| Bone marrow suppression | Radiation effect on bone marrow, especially with repeated high-dose RAI | Leukopenia, thrombocytopenia (usually mild and transient) |
| Infertility/gonadal damage | ¹³¹I radiation to gonads; cumulative effect with repeated doses | Transient oligospermia in men; transient ovarian dysfunction in women. Avoid pregnancy for 1 year post-RAI [2] |
| Secondary malignancies | Long-term stochastic radiation effect; cumulative dose-dependent | Leukaemia (AML), breast cancer, bladder cancer (very small absolute risk, usually only with cumulative doses > 600 mCi) |
| Lacrimal gland damage | NIS expression in lacrimal glands → ¹³¹I concentration → radiation damage | Dry eyes, epiphora (paradoxical tearing from nasolacrimal duct stenosis) |
| Pulmonary fibrosis | Only with diffuse lung metastases treated with very high-dose RAI — radiation to lung parenchyma | Cough, dyspnoea, restrictive pattern on PFTs. Rare |
Chronic supraphysiological T4 dosing creates a state of iatrogenic subclinical hyperthyroidism, which carries long-term risks:
| Complication | Mechanism | Clinical Relevance |
|---|---|---|
| Osteoporosis | Excess thyroid hormone accelerates bone turnover → net bone resorption > bone formation. Particularly affects postmenopausal women (compounded by oestrogen deficiency) | Calcium supplementation required [2]; monitor bone mineral density (DEXA) |
| Atrial fibrillation | Thyroid hormone increases cardiac β-adrenergic receptor sensitivity and shortens atrial refractory period → facilitates re-entrant circuits | May need to relax TSH suppression target in elderly patients or those with pre-existing cardiac disease [2] |
| Cardiac dysfunction | Chronic sympathetic overdrive → left ventricular hypertrophy, diastolic dysfunction | Particularly relevant in elderly; balance cancer recurrence risk vs cardiac risk |
| Anxiety, insomnia, tremor | Systemic effects of chronic mild hyperthyroidism | Quality of life impact |
This is why the low-risk group does NOT require TSH suppression [3] — the marginal benefit of suppression in low-risk patients is outweighed by the cumulative cardiovascular and skeletal harm from decades of subclinical hyperthyroidism.
This is a high-yield exam scenario: a patient develops respiratory distress in the recovery room after thyroidectomy. What is the differential? Think systematically [3]:
| Cause | Mechanism | Key Features | Management |
|---|---|---|---|
| Post-operative haematoma | Expanding haematoma → venous compression → laryngeal oedema → airway obstruction | Tense, expanding neck swelling; progressive dyspnoea developing over hours | Open wound at bedside; evacuate haematoma; intubate [1] |
| Bilateral RLN injury | Both vocal cords paralysed in adducted position → glottic obstruction | Stridor immediately upon extubation; no tense swelling | Re-intubation ± tracheostomy [1][3] |
| Laryngospasm from hypocalcaemia | Acute hypocalcaemia → hyperexcitable laryngeal muscles → spasm closing the glottis | Usually later onset (12–72 hours); perioral numbness precedes; low serum Ca²⁺ | IV calcium gluconate; secure airway [3] |
| Tracheomalacia | Floppy tracheal wall collapses post-operatively after removal of chronic extrinsic compression by large goitre | Stridor on inspiration; develops after extubation | Positive pressure ventilation; tracheostomy if severe |
| Tracheal/oesophageal injury | Surgical trauma; pneumothorax if tracheal perforation communicates with pleura | Subcutaneous emphysema; respiratory distress | Primary surgical repair |
| Pneumothorax | Rare; can occur with extensive lateral neck dissection or substernal goitre surgery | Absent breath sounds on one side; tracheal deviation | Chest drain (tube thoracostomy) |
| Type | 5-Year Survival | Key Prognostic Factors |
|---|---|---|
| Papillary CA | Low risk: 95%; Intermediate: 88%; High risk: 50% [2] | Age, tumour size, ETE, LN mets, distant mets, histological variant, BRAF mutation |
| Follicular CA | Similar to PTC, slightly worse [2] | Degree of vascular invasion (extensive > 4 foci = worse), distant mets |
| Medullary CA | 60–70% [1] | Calcitonin level, completeness of resection, MEN2 vs sporadic, nodal involvement |
| Anaplastic CA | Median survival < 6 months [1][7] | Universally poor; no effective treatment reverses prognosis |
| Thyroid lymphoma | Median survival 9 years [1] | Better than anaplastic; responds to R-CHOP + EBRT |
Prognostic scoring — MACIS system (for papillary CA) [2]:
- M — Metastasis
- A — Age
- C — Completeness of resection
- I — Invasion (extrathyroidal extension)
- S — Size
High Yield Summary
Surgical complications by timing:
- Immediate: haemorrhage, RLN injury (unilateral = hoarseness; bilateral = airway obstruction), SLN injury (loss of high pitch), thyroid storm, tracheomalacia.
- Early: haematoma (emergency — open wound at bedside), seroma, wound infection, dysphagia.
- Late: hypoparathyroidism/hypocalcaemia (MOST common), hungry bone syndrome, hypothyroidism, recurrence, keloid.
Hypocalcaemia: CATS GO NUMB. Check Chvostek/Trousseau signs. Acute Mx: IV calcium gluconate. Maintenance: oral calcium + calcitriol (NOT cholecalciferol — need active vitamin D because PTH is absent).
Bilateral RLN injury: 6 adductors > 2 abductors → cords adduct → airway obstruction → emergency re-intubation/tracheostomy.
Post-op dyspnoea DDx: haematoma, bilateral RLN injury, laryngospasm (hypocalcaemia), tracheomalacia, pneumothorax.
RAI complications: sialadenitis, infertility (avoid pregnancy 1 year), secondary malignancies (very rare).
TSH suppression complications: osteoporosis, AF, cardiac dysfunction — low-risk patients do NOT need suppression.
Active Recall - Complications of Thyroid Cancer and Treatment
References
[1] Senior notes: Ryan Ho Endocrine.pdf (pp. 22, 33–38 — complications of thyroidectomy, other thyroid cancers) [2] Senior notes: felixlai.md (Thyroid cancer sections V, IX — complications of thyroidectomy pp. 1010–1014) [3] Senior notes: maxim.md (Thyroidectomy complications, post-op dyspnoea DDx, parathyroid injury) [7] Lecture slides: GC 177. A thyroid nodule benign thyroid nodules; thyroid cancer.pdf (pp. 22, 24, 27, 28) [9] Lecture slides: Management of differentiated thyroid carcinoma.pdf (p. 11 — ATA risk stratification)
High Yield Summary
Definition: Malignant neoplasm of the thyroid; most commonly papillary carcinoma (80-90%) from follicular epithelial cells.
Epidemiology (HK): 2.6% of all cancers, 5th most common in females, M:F ~1:3-4, increasing incidence, very low mortality.
Key Risk Factors: Female sex, head/neck irradiation (especially NPC treatment in HK), family history, MEN2 syndrome, FAP (papillary), Hashimoto's (lymphoma), iodine deficiency (follicular).
Molecular: MAPK pathway (RET-RAS-BRAF) is central. BRAF V600E in papillary; RAS/PAX8-PPARγ in follicular; RET germline mutations in familial MTC; TP53 in anaplastic.
Clinical Features — Red Flags for Malignancy: Solitary hard fixed nodule, progressive growth, male sex, age < 14 or > 70, hoarseness (RLN invasion), Level VI lymphadenopathy, prior radiation, FHx.
Papillary CA: Most common, lymphatic spread, psammoma bodies, Orphan Annie nuclei, excellent prognosis.
Follicular CA: Haematogenous spread (bone, lung), FNAC cannot diagnose (need histology for capsular/vascular invasion), good prognosis.
Medullary CA: C-cell origin, calcitonin marker, amyloid on histology, MEN2 association, prophylactic thyroidectomy for RET carriers.
Anaplastic CA: De-differentiated, rapidly lethal (< 6 months), no RAI uptake, palliative management.
High Yield Summary
DDx framework: Organise by functional status (hyperthyroid → think hot nodule/toxic adenoma; euthyroid → most common, benign vs malignant; hypothyroid → Hashimoto's ± lymphoma risk).
Most thyroid nodules are benign (~85–90%): colloid cyst, follicular adenoma, MNG, Hashimoto's pseudonodule.
Primary thyroid malignancies: Papillary (most common, lymphatic spread, psammoma bodies), Follicular (haematogenous, FNAC cannot diagnose), Medullary (C-cells, calcitonin, MEN2), Anaplastic (rapidly lethal, de-differentiated), Lymphoma (Hashimoto's background, needs core biopsy).
Metastatic to thyroid: RCC is the most common primary.
Red flags for malignancy: Male, age extremes, solitary hard fixed nodule, hoarseness, Level VI LN, radiation history, FHx, cold on scintigraphy, SHIT CME on USG.
Critical DDx pitfall: Follicular adenoma vs carcinoma — indistinguishable on FNAC; requires surgical excision for histological capsular/vascular invasion.
Rapidly enlarging thyroid: DDx = haemorrhagic cyst, anaplastic CA, thyroid lymphoma, subacute thyroiditis.
Hot nodule on scintigraphy: Rarely malignant → does NOT need FNAC.
High Yield Summary
Investigation hierarchy: TFT (TSH) → USG → FNAC (± scintigraphy if TSH suppressed).
TSH is the first test: Suppressed → scintigraphy; Normal/elevated → USG ± FNAC directly.
USG suspicious features (SHIT CME): Solid, Hypoechoic, Irregular margins, Taller-than-wide, Chaotic central vascularity, Microcalcifications, Extrathyroidal extension.
FNAC is the single most important investigation: Bethesda classification guides management. Cannot diagnose follicular CA (need histological capsular/vascular invasion). Cannot diagnose lymphoma (need core biopsy).
Hot nodule on scintigraphy = almost never malignant → NO FNAC needed. Cold nodule = 10–20% malignancy risk → needs FNAC.
Bethesda IV (follicular neoplasm): Diagnostic hemithyroidectomy — final diagnosis requires histological capsular/vascular invasion.
Pre-op for MTC: RET mutation, calcitonin, CEA, 24h urine metanephrines, Ca/PTH.
Iodinated contrast CT can interfere with subsequent RAI scan/therapy — plan accordingly.
TNM staging: Age < 55 with DTC → max Stage II. Anaplastic → auto Stage IV.
High Yield Summary
Surgical decision: HemiT for low-risk DTC ( < 4 cm, no ETE, N0); TT for high-risk DTC ( > 4 cm, ETE, N1, M1, aggressive histology); TT for ALL MTC; palliative for anaplastic.
LN dissection: Papillary — therapeutic CCD/LCD, prophylactic CCD only for advanced disease. MTC — prophylactic CCD for ALL. Follicular — usually not required.
Pre-op essentials: Euthyroid status, laryngoscopy (vocal cords), Ca/VitD, rule out phaeo in MTC.
T4 post-op: Dual role (replacement + TSH suppression). Low risk: TSH 0.5–2.0; Intermediate: 0.1–0.5; High: < 0.1. MTC: euthyroid only, no suppression.
RAI: Exploits NIS expression in DTC. Not for MTC or anaplastic. Preparation: low-iodine diet, T4 withdrawal (or rhTSH), avoid pregnancy 1 year post-RAI. Low-risk DTC does NOT need RAI.
EBRT: For R2 (macroscopic residual), incomplete resection, anaplastic CA.
Targeted therapy: Lenvatinib/sorafenib for RAI-refractory DTC; selpercatinib/vandetanib/cabozantinib for MTC; dabrafenib+trametinib for BRAF V600E anaplastic CA.
Surveillance: USG Q6m, Tg Q3–6m, calcitonin/CEA for MTC, RAI WBS at 6–12m post-RAI.
High Yield Summary
Surgical complications by timing:
- Immediate: haemorrhage, RLN injury (unilateral = hoarseness; bilateral = airway obstruction), SLN injury (loss of high pitch), thyroid storm, tracheomalacia.
- Early: haematoma (emergency — open wound at bedside), seroma, wound infection, dysphagia.
- Late: hypoparathyroidism/hypocalcaemia (MOST common), hungry bone syndrome, hypothyroidism, recurrence, keloid.
Hypocalcaemia: CATS GO NUMB. Check Chvostek/Trousseau signs. Acute Mx: IV calcium gluconate. Maintenance: oral calcium + calcitriol (NOT cholecalciferol — need active vitamin D because PTH is absent).
Bilateral RLN injury: 6 adductors > 2 abductors → cords adduct → airway obstruction → emergency re-intubation/tracheostomy.
Post-op dyspnoea DDx: haematoma, bilateral RLN injury, laryngospasm (hypocalcaemia), tracheomalacia, pneumothorax.
RAI complications: sialadenitis, infertility (avoid pregnancy 1 year), secondary malignancies (very rare).
TSH suppression complications: osteoporosis, AF, cardiac dysfunction — low-risk patients do NOT need suppression.
Thyroglossal Duct Cyst
A congenital midline neck cyst arising from remnants of the thyroglossal duct, typically presenting as a painless, mobile mass that elevates with swallowing or tongue protrusion.
Thyroid Nodule Workup (uss + Bethesda Fnac)
Thyroid nodule workup involves ultrasound assessment of nodule features followed by fine needle aspiration cytology classified using the Bethesda system (categories I–VI) to stratify malignancy risk and guide management.