GC177 A Thyroid Nodule Benign Thyroid Nodules; Thyroid Cancer
Thyroid nodules are discrete lesions within the thyroid gland, classified as benign (colloid nodules, adenomas) or malignant (papillary, follicular, medullary, or anaplastic carcinoma), evaluated by ultrasound characteristics and fine-needle aspiration cytology.
A Thyroid Nodule: Benign Thyroid Nodules & Thyroid Cancer
The Big Idea: A thyroid nodule is one of the most common clinical presentations you will encounter. The central clinical question is always: is this nodule benign or malignant? This lecture walks you through prevalence, classification of goitres, pathology of thyroid nodules, investigations (USG, FNAC with Bethesda classification, molecular testing, isotope scan), management of benign nodules (surgical and non-surgical ablative), and then dives into thyroid cancer — histologic types, management of well-differentiated thyroid carcinoma (WDTC) including extent of surgery, lymph node dissection, adjuvant radioiodine therapy, the special case of papillary thyroid microcarcinoma (PTMC), and the less common medullary and anaplastic carcinomas.
Learning Objectives:
- Understand the epidemiology and prevalence of thyroid nodules
- Classify goitres systematically
- Know the pathological differential of a thyroid nodule
- Master the investigation algorithm: TFT → USG → FNAC (Bethesda) → molecular testing / isotope scan
- Know the indications for treating benign nodules and the surgical options
- Understand non-surgical ablative treatments and their limitations
- Classify thyroid carcinomas by histologic type
- Manage well-differentiated thyroid carcinoma: surgery, lymph node dissection, adjuvant therapy
- Understand low-risk vs high-risk WDTC and the controversy around PTMC management
- Know the key features and management of medullary and anaplastic thyroid carcinoma
How it fits: This lecture integrates with GC 218 (Neck mass), GC 063 (Thyrotoxicosis/hypothyroidism), GC 216 (Dysphonia — recurrent laryngeal nerve injury post-thyroidectomy), nuclear medicine imaging, and the Endocrine block. It is a favourite in summative exams — thyroid nodule MCQs and minicases appear nearly every year.
Core Concepts and Mechanisms
Thyroid nodules are extraordinarily common. Prevalence depends on iodine deficiency, ionizing radiation, gender, age, and method of detection. [1]
- Palpation detects nodules in only 3–7% of the population
- Ultrasound or autopsy studies reveal nodules in > 30–50% of adults
- This massive discrepancy is clinically important: most nodules are subclinical and incidental. The challenge is identifying the ~10% that harbour malignancy among this sea of benign nodules.
Why does method matter for exams? Because USG is NOT recommended as a screening test in healthy individuals — its high sensitivity would pick up enormous numbers of clinically insignificant nodules, leading to overinvestigation and overtreatment. [1]
Thyroid cancer incidence has been rising but mortality and stage at diagnosis remain stable. [1]
This is driven by overdiagnosis — improved imaging (USG, CT, PET) detects small papillary microcarcinomas that would never have caused harm. This is the rationale behind active observation for PTMC.
Goitre Classification: [1]
- Neoplastic goitre — benign or malignant
- Thyroiditis — bacterial (acute suppurative), viral (subacute), lymphocytic/Hashimoto/autoimmune (chronic)
- Simple goitre (endemic or sporadic) — diffuse or nodular
- Toxic goitre — diffuse toxic (Graves'), toxic nodular (Plummer's), toxic/functioning adenoma
| Category | Subtypes | Key Feature |
|---|---|---|
| Simple goitre | Diffuse, Nodular | Euthyroid; endemic = iodine deficiency; sporadic = goitrogens, physiological |
| Toxic goitre | Graves' (diffuse), Plummer's (toxic MNG), Toxic adenoma | Hyperthyroid |
| Thyroiditis | Acute (bacterial), Subacute (viral/de Quervain), Chronic (Hashimoto's) | Inflammatory; subacute = painful + raised ESR |
| Neoplastic | Benign (follicular adenoma), Malignant (papillary, follicular, medullary, anaplastic) | Need FNAC to distinguish |
Pathology breakdown: [1]
- Nodular goitre (colloid / haemorrhagic cystic / complex / hyperplastic / adenomatous nodule) — 70%
- Benign follicular adenoma (mainly non-toxic) — 15%
- Well-differentiated thyroid carcinoma — 10%
- Miscellaneous (other malignancies, thyroiditis) — 5%
Why this matters: When a patient presents with a thyroid nodule, the most likely diagnosis is a benign nodular goitre (70%). This is the basis for MCQ Q66 in the 2024 paper — the most likely pathology of a clinically solitary thyroid nodule is benign nodular goitre, NOT follicular adenoma or carcinoma. [2]
Exam Trap
A "clinically solitary" thyroid nodule does NOT mean it's a true solitary neoplasm. USG often reveals additional nodules not felt on palpation. The most common pathology is still a dominant nodule within a nodular goitre (70%), not a follicular adenoma (15%) or carcinoma (10%).
Thyroid nodule presentations: [1]
- Neck swelling/mass
- Pain or discomfort
- Local pressure symptoms / voice change (dysphonia, dysphagia, dyspnoea)
- Thyroid dysfunction (hyper- or hypothyroid symptoms)
- Incidental or unrelated — found on physical examination or imaging (USG, CXR, CT, PET)
Clinical Features Suggesting Malignancy
From the lecture and senior notes: [1][3][4]
| Feature | Why It Suggests Malignancy |
|---|---|
| Male sex | Nodules less common in males but higher malignancy rate |
| Age < 14 or > 70 | Extremes of age = higher risk |
| Solitary/dominant nodule | Higher risk than multiple nodules |
| Hard, fixed, irregular | Invasion of surrounding tissue |
| Progressive growth over weeks–months | Active neoplasm rather than stable benign nodule |
| Hoarseness (RLN palsy) | Invasion of recurrent laryngeal nerve |
| Cervical lymphadenopathy (esp. level VI) | Nodal metastasis — first echelon drainage |
| History of neck irradiation | Strong risk factor for papillary carcinoma |
| FHx of thyroid cancer | Medullary (~20% familial via MEN2), papillary (~5% familial) |
| Rapid painful enlargement | Anaplastic carcinoma, haemorrhage into cyst, or lymphoma |
Investigations — The Algorithm
Core investigations: [1]
- Blood tests: TSH + free T4
- Ultrasound
- FNAC (± molecular testing)
Additional investigations:
- ESR, thyroid antibodies, calcitonin, genetic testing
- Imaging: radioisotope scan, CT/MRI, PET scan
- Endoscopy
- Thyroidectomy (diagnostic + therapeutic)
Why first? TSH determines the next step:
- Low TSH → possible toxic nodule → order thyroid scintigraphy to determine if nodule is "hot" (functioning)
- Normal or high TSH → proceed to USG → FNAC
Hot (hyperfunctioning) nodules are rarely malignant and do NOT require FNAC. [1][5][6] Cold (hypofunctioning) nodules have a 10–20% risk of malignancy and require FNAC. [5][6]
2. Ultrasonography (USG)
USG is non-invasive, no radiation, convenient and cheap, with high sensitivity but relatively low specificity. [1] Roles:
- Extend physical examination
- Select nodules for FNAC
- Guide needle aspiration
- For ALL patients with goitre/palpable nodule
- NOT recommended as a screening test [1]
| Letter | Feature | Why Suspicious |
|---|---|---|
| S | Solid nodule | Cystic/spongiform nodules are usually benign |
| H | Hypoechoic | Malignant cells are more cellular → less echogenic |
| I | Irregular margin | Suggests infiltrative growth |
| T | Taller than wide (AP > TS) | Perpendicular growth pattern against tissue planes = infiltrative |
| C | Chaotic central vascularity | Neoangiogenesis of tumour |
| M | Microcalcifications | Psammoma bodies (pathognomonic of papillary carcinoma) |
| E | Extrathyroidal extension | Direct invasion beyond thyroid capsule |
| Sonographic Pattern | Features | Malignancy Risk | FNA Size Cutoff |
|---|---|---|---|
| High suspicion | Solid hypoechoic + microcalcifications / taller-than-wide / irregular margins / ETE | > 70–90% | ≥ 1 cm |
| Intermediate suspicion | Hypoechoic solid, no high-risk features | 10–20% | ≥ 1 cm |
| Low suspicion | Isoechoic/hyperechoic, partially cystic with eccentric solid areas | 5–10% | ≥ 1.5 cm |
| Very low suspicion | Spongiform or partially cystic without suspicious features | < 3% | ≥ 2 cm |
| Benign | Purely cystic, no solid component | < 1% | No FNA |
Bethesda Classification for Reporting Thyroid Cytopathology: [1]
| Bethesda Category | Diagnostic Category | Risk of Malignancy (%) | Usual Management |
|---|---|---|---|
| I | Non-diagnostic | 1–4 | Repeat FNA |
| II | Benign | 0–3 | Clinical follow-up |
| III | AUS / FLUS | 5–15 | Repeat FNA |
| IV | Follicular neoplasm | 15–30 | Surgical lobectomy |
| V | Suspicious of malignancy | 60–75 | Surgical lobectomy (± frozen section) → total thyroidectomy |
| VI | Malignant | 97–99 | Total thyroidectomy |
Key points:
- AUS = atypia of undetermined significance; FLUS = follicular lesion of undetermined significance [1]
- Category IV (follicular neoplasm): FNAC cannot distinguish follicular adenoma from follicular carcinoma — this requires histological demonstration of capsular or vascular invasion on the excised specimen. Hence, diagnostic lobectomy is needed. [7]
- Category V: Lobectomy with intraoperative frozen section — if malignancy confirmed → complete to total thyroidectomy
- Core needle biopsy is NOT performed on thyroid — risk of massive bleeding from this highly vascular organ [5][6]
High Yield — FNAC Cannot Diagnose Follicular Carcinoma
FNAC looks at individual cell morphology. Follicular adenoma and follicular carcinoma have identical cytological appearances. The diagnosis of follicular carcinoma requires histological evidence of capsular invasion or vascular invasion — which can only be assessed on the resected specimen. This is why Bethesda IV goes straight to surgical lobectomy, not repeat FNA.
Molecular testing for indeterminate nodules (Bethesda III–IV): [1]
- BRAF mutation: found in 40–64% of papillary carcinomas; not sensitive but specific = high PPV → "rule-in" test
- Gene expression classifiers (Afirma GSC, ThyroSeq v3): highly sensitive but not specific = high NPV → "rule-out" test
- Can avoid diagnostic thyroidectomy in ~50% of indeterminate nodules
Why this matters: For a Bethesda III or IV nodule, if molecular testing shows a benign profile (high NPV rule-out test), you can safely observe rather than operate. If BRAF is positive (high PPV rule-in test), you proceed to surgery with confidence.
I-123 or Tc-99m scan: [1]
- Low sensitivity and specificity for diagnosing malignancy
- Main role: functional assessment in thyrotoxic patients (low TSH)
- Differentiates: Graves' (diffuse uptake) vs Toxic adenoma (focal hot with suppressed rest) vs Toxic MNG (heterogeneous uptake)
| Scan Pattern | Diagnosis |
|---|---|
| Diffuse increased uptake | Graves' disease |
| Focal hot nodule with suppressed background | Toxic adenoma |
| Heterogeneous uptake with multiple hot/cold areas | Toxic multinodular goitre |
| Cold nodule | Suspicious — 10–20% malignancy risk → needs FNAC |
| Diffusely decreased uptake | Thyroiditis, T4 overdose, iatrogenic |
PET scan has NO diagnostic role in thyroid diseases — even malignant nodules can have low uptake. [7]
- CXR (thoracic inlet view): assess tracheal deviation, retrosternal extension
- CT/MRI: retrosternal extension, staging of advanced cancer (NOT routine)
- Caution: iodinated CT contrast can interfere with subsequent radioactive iodine scan/therapy [4]
- Endoscopy: direct laryngoscopy to assess vocal cord function (RLN palsy) — should be done pre-operatively
- Calcitonin: if medullary thyroid carcinoma suspected
- ESR, thyroid antibodies: if thyroiditis suspected
Management of Benign Thyroid Nodules
Indications for treating benign thyroid nodules: [1]
- Symptomatic (size of goitre/nodule)
- Increase in goitre size
- Trachea compression or deviation
- Retrosternal extension
- Suspected malignancy
- Cosmetic considerations / patient wish
Surgical options: [1]
| Operation | Indication | Advantages | Disadvantages |
|---|---|---|---|
| Unilateral lobectomy (hemithyroidectomy) | Uninodular goitre | Safe, minimal morbidity, diagnostic + curative; future contralateral surgery easy | 10–20% chance of hypothyroidism |
| Total/near-total thyroidectomy | Symptomatic multinodular goitre | No recurrence/reoperation needed | Additional risk (hypoparathyroidism); needs lifelong thyroxine replacement |
| Partial/bilateral subtotal thyroidectomy | Rarely indicated | — | Risk of recurrence, difficult reoperation |
Why lobectomy for uninodular disease? It preserves the contralateral lobe's function (only 10–20% develop hypothyroidism), avoids the risks of bilateral surgery (bilateral RLN injury → airway compromise, hypoparathyroidism), and still provides histological diagnosis.
Why total thyroidectomy for MNG? Bilateral disease cannot be adequately treated by removing one lobe. Subtotal thyroidectomy leaves tissue that can regrow and require dangerous reoperation in a scarred field.
This is extremely high-yield and tested in past minicases (e.g., 2022 Minicase Case 2 Section 4): [8]
| Timing | Complication | Mechanism |
|---|---|---|
| Immediate (0–24h) | Reactionary haemorrhage / neck haematoma | Bleeding → airway compression → EMERGENCY: open wound at bedside, evacuate clot |
| Early (days) | Hypocalcaemia (transient hypoparathyroidism) | Parathyroid gland devascularization or inadvertent removal |
| Recurrent laryngeal nerve injury → hoarseness | Intraoperative stretch/transection | |
| Late | Permanent hypoparathyroidism | Complete devascularization of all 4 glands |
| Hypothyroidism | Expected after total thyroidectomy → needs lifelong T4 | |
| Keloid scar | Cosmetic issue |
Post-thyroidectomy Monitoring
After total thyroidectomy, the surgical drain monitors for haematoma. The purpose of the drain is to prevent airway obstruction by releasing pressure and to reduce haematoma formation — this was tested in 2025 MCQ Q53. [9] Check calcium levels at 6–12 hours post-op. Symptoms of hypocalcaemia: perioral tingling, Chvostek sign, Trousseau sign, carpopedal spasm.
Non-surgical ablative options: [1]
- Ethanol injection (PEI) — for cystic/predominantly cystic nodules (cytoplasmic protein dehydration and coagulation necrosis)
- Radiofrequency ablation (RFA)
- High-intensity focused ultrasound (HIFU)
- Percutaneous laser ablation (LA)
- Microwave ablation (MWA) — RFA, HIFU, LA, MWA work by thermal coagulation necrosis — for complex or solid nodules
Volume reduction rate (VRR): 50–80%. [1] Patient selection criteria:
- Symptomatic / single / hyperfunctioning nodule
- < 4 cm or 20 mL / growth on sonogram
- Benign (FNAC × 2)
- Motivated patients
Expectations: preserve function, minimally invasive, avoid GA, day procedure, scarless, cosmetic outcome [1] Limitations: not curative, unsatisfactory shrinkage, regrowth, need for additional procedures, unique risks, expense [1]
Major histologic types: [1]
| Type | Frequency | Key Features |
|---|---|---|
| Papillary carcinoma (PTC) | ~90% of WDTC; ~81% of all thyroid CA | Psammoma bodies, lymphatic spread to cervical LN, multifocal/bilateral, excellent prognosis |
| Follicular carcinoma | ~10% of WDTC | Haematogenous spread (bone, lung), requires capsular/vascular invasion for dx |
| Poorly differentiated (insular) | < 5% | Intermediate behaviour |
| Undifferentiated (anaplastic) | < 5% | Rapidly fatal, elderly, locally advanced |
| Medullary carcinoma | < 5% | C-cells, calcitonin, 1/3 familial (MEN2), RET proto-oncogene |
| Others | ~1% | Lymphoma, SCC, sarcoma, metastasis |
Well-Differentiated Thyroid Carcinoma (WDTC) — Risk Stratification
Risk Groups: [1]
| Low Risk | High Risk | |
|---|---|---|
| % of patients | 85–90% | 10–15% |
| Mortality (10–20 yrs) | 2–5% | 40–50% |
| Recurrence | 10% | 45% |
Why this stratification matters: It drives the extent of surgery, need for RAI, and intensity of follow-up.
Management of Papillary Thyroid Carcinoma (PTC)
For low-risk early-stage PTC (< 4 cm, no invasion, no LN metastasis): [1]
| Total Thyroidectomy | Hemithyroidectomy |
|---|---|
| Commonly multifocal and bilateral | Excellent survival and low recurrence |
| Allows RAI ablation and thyroglobulin (Tg) monitoring | Avoids T4 replacement |
| Low morbidity by experienced surgeons | Lower morbidity overall |
The debate: Overtreatment/surgical risk vs. avoiding recurrence and facilitating follow-up. The trend is toward personalized treatment based on patient and physician preference. [1]
Current ATA guidelines (simplified):
- < 1 cm, no ETE, no LN mets, no high-risk features: lobectomy is sufficient (or even active observation for PTMC)
- 1–4 cm, low risk: lobectomy OR total thyroidectomy
- > 4 cm, or any high-risk features (ETE, LN mets, distant mets, aggressive histology): total thyroidectomy
Central compartment (Level VI): [1]
- Same incision as thyroidectomy
- Prophylactic/routine vs therapeutic — controversial
- Reduces disease recurrence and reoperation
- But: upstages disease → increased use of RAI; increased morbidity (hypoparathyroidism)
Lateral compartment (Level II–V): [1]
- Usually therapeutic only (not prophylactic)
- Clinically involved or FNAC-proven nodes
- Preferred: modified/functional/selective neck dissection (NOT "berry-picking" excisional)
Why not berry-picking? Incomplete removal leaves behind microscopic disease. Formal compartmental dissection provides better locoregional control.
Use of I-131 ablation: [1]
- Follows total/near-total thyroidectomy
- Preparation: thyroxine withdrawal vs recombinant TSH (Thyrogen)
- Therapy (high-risk stage III/IV): gross residual disease, nodal or distant metastases
- Ablation (selected low-risk stage I/II): destroy occult microscopic foci, facilitate surveillance
- Low dose (30 mCi) as effective as higher dose (100 mCi) for ablation in low-risk patients
- Short and long-term adverse effects (sialadenitis, lacrimal duct obstruction, secondary malignancy with high cumulative doses)
Why RAI works in thyroid cancer: Well-differentiated follicular and papillary cells retain the ability to trap iodine via the sodium-iodide symporter (NIS). RAI exploits this to selectively irradiate residual thyroid tissue and metastases. TSH stimulation (either by T4 withdrawal or Thyrogen injection) upregulates NIS expression, increasing RAI uptake.
After total thyroidectomy for WDTC:
- T4 replacement is mandatory (no thyroid tissue left)
- In cancer patients, the dose is titrated to suppress TSH below normal range (because TSH stimulates growth of residual differentiated thyroid cancer cells)
- Target TSH depends on risk: high-risk → TSH < 0.1 mIU/L; low-risk → TSH 0.1–0.5 mIU/L
- Monitor for iatrogenic thyrotoxicosis side effects: AF, osteoporosis (especially in postmenopausal women)
- After total thyroidectomy + RAI ablation, there should be no thyroid tissue → Tg should be undetectable
- Rising Tg = recurrent/persistent disease → triggers imaging workup (USG neck, diagnostic RAI whole body scan, CT, PET-CT)
- Anti-Tg antibodies can interfere with Tg assay → must be checked simultaneously
Papillary Thyroid Microcarcinoma (PTMC)
Definition (WHO): < 1 cm + detected incidentally [1]
- Usually pT1a or stage I disease
- Low-risk or extremely low-risk
- Excellent or almost 100% survival
- Less aggressive treatment (lobectomy) or active observation
Active observation criteria: [1]
- Biopsy-proven incidental PTMC
- No metastases / invasion / high-grade subtype
- Tumour progression (up to 20 years):
- ↑ size ≥ 3 mm: 8%
- Novel nodal metastases: 3.5%
- Surgical treatment offered for tumour progression
- Feasible treatment option
Meta-analysis and propensity-matched analysis show: [1]
- Complete ablation / volume reduction / safety
- Tumour progression, recurrence, nodal metastasis same as surgery
- Possibly another alternative for PTMC without metastasis
Key Exam Point — PTMC Management
For biopsy-proven PTMC < 1 cm with no mets, no ETE, no high-grade subtype: active observation is a valid option. This is the trend toward de-escalation of treatment for low-risk thyroid cancer to avoid overtreatment.
- Calcitonin (basal/stimulated) as tumour marker
- Total thyroidectomy + central ± lateral neck dissection
- 1/3 familial:
- MEN IIA: MTC + phaeochromocytoma + parathyroid hyperplasia
- MEN IIB: MTC + phaeochromocytoma + mucosal neuromas / ganglioneuromatosis
- Familial MTC (isolated)
- Genetic analysis: RET proto-oncogene
- Prophylactic thyroidectomy in carriers (age 5–10 yrs)
Why calcitonin? MTC arises from parafollicular C-cells that secrete calcitonin. This makes calcitonin both a diagnostic marker and a post-operative surveillance tool. CEA is also elevated in ~80%.
Why screen family members? MEN2 follows autosomal dominant inheritance of RET proto-oncogene mutations. Affected carriers have near 100% lifetime risk of MTC → prophylactic thyroidectomy in childhood saves lives.
Important: MTC does NOT respond to RAI (C-cells don't trap iodine — only follicular cells do). T4 suppression is also NOT needed — just replace to euthyroid state. [4]
- Elderly with poor comorbid state
- Aggressive and rapidly growing
- Locally advanced disease at presentation
- Frequent distant metastases
- Lack of effective treatment
- Chemoirradiation + resection + targeted therapy
- Invariably palliative and fatal (median survival < 6 months)
Why so aggressive? These tumours are completely dedifferentiated — they lose all thyroid-specific features (no iodine trapping, no thyroglobulin production). They don't respond to RAI or TSH suppression. Often arise from pre-existing long-standing goitre or prior differentiated carcinoma that has undergone dedifferentiation.
| Feature | Papillary | Follicular | Medullary | Anaplastic |
|---|---|---|---|---|
| Cell of origin | Follicular | Follicular | Parafollicular C-cell | Dedifferentiated |
| Frequency | ~81% | ~10% | < 5% | < 5% |
| Peak age | 30–50 | 40–60 | 50+ (sporadic), 20–30 (familial) | 60–70 |
| Spread | Lymphatic → cervical LN | Haematogenous → bone, lung | Both (early LN + distant) | Local invasion + distant |
| Histological hallmark | Psammoma bodies, nuclear grooves, Orphan Annie eyes | Capsular/vascular invasion | Amyloid stroma | Pleomorphic giant cells |
| FNAC diagnostic? | Yes | No (need lobectomy) | Yes (calcitonin) | Yes |
| Tumour marker | Thyroglobulin | Thyroglobulin | Calcitonin, CEA | None useful |
| RAI responsive? | Yes | Yes | No | No |
| TSH suppression? | Yes | Yes | No (replace to euthyroid) | No |
| Genetic | BRAF, RAS | RAS, PAX8-PPARγ | RET proto-oncogene | TP53, BRAF, RAS |
| Prognosis | Excellent (> 95% 10-yr) | Good (> 80% 10-yr) | Moderate (60–70% 5-yr) | Fatal (< 6 mo median) |
| Familial | ~5% | Rare | ~20–33% (MEN2) | No |
Common Exam Traps
-
"Most likely pathology of a clinically solitary thyroid nodule" → Answer is benign nodular goitre (70%), NOT follicular adenoma (15%) or carcinoma. Many students pick follicular adenoma because "solitary" sounds neoplastic, but nodular goitre can present as a dominant nodule.
-
"Investigation to differentiate toxic adenoma from Graves' with nodule" → Thyroid scintigraphy (isotope scan). USG and FNAC cannot determine function.
-
"Can FNAC diagnose follicular carcinoma?" → No. FNAC cannot assess capsular/vascular invasion. Needs lobectomy for histology.
-
"Why drain after thyroidectomy?" → To reduce haematoma and prevent airway obstruction (NOT to monitor thyroxine levels or deliver antibiotics). [9]
-
"Hot nodule — next step?" → Treat as toxic adenoma. Do NOT perform FNAC (hot nodules are almost never malignant).
-
"Central neck mass that moves with swallowing in a 40-year-old lady" → Most likely papillary thyroid carcinoma (in the context of EMQ with thyroid options) or thyroid pathology in general. This exact stem appears in 2021 MCQ Q9 and 2025 MCQ Q24. [10][9]
-
"Medullary thyroid carcinoma" → Think calcitonin + CEA + RET + MEN2. This was tested in 2023 MCQ Q6 with paroxysmal symptoms (consider concurrent phaeochromocytoma in MEN2). [11]
-
"Acute onset thyroid swelling over 2 days after coughing" → Thyroid haemorrhagic cyst (haemorrhage into pre-existing nodule/cyst). Not anaplastic carcinoma (which grows over weeks, not 2 days). [11]
Past Paper Questions
Stem: A 65-year-old lady with a palpable nodular goitre complained of thyrotoxic symptoms. Two of her siblings had a similar history. FNAC showed cytologically benign follicles. Answer: J. Toxic multinodular goitre — Nodular goitre + thyrotoxicosis + FHx of similar problem + benign FNAC = Plummer's disease (toxic MNG)
Stem: A 40-year-old gentleman with ESRF on dialysis presented with a right-sided neck swelling. FNAC revealed atypical cells with nuclear enlargement, grooves and inclusions. Answer: G. Papillary thyroid carcinoma — Nuclear grooves and inclusions (Orphan Annie nuclei) are pathognomonic of PTC. ESRF/dialysis patients have increased risk of thyroid nodules.
Stem: 40-year-old lady with neck swelling × 6 months, moves with swallowing, thyrotoxic symptoms (weight loss, tremor, palpitations), TSH < 0.03, T4 = 45 pmol/L. USG: 2.5 cm hypoechoic regular nodule left lower pole. FNAC: hyperplastic nodule. Thyroid scan: increased activity left lower pole, normal right. Questions asked:
- Investigations to rule out malignancy → USG + FNAC
- Comment on thyroid status → Overt hyperthyroidism (suppressed TSH, elevated fT4)
- DDx of thyroid nodule + hyperthyroidism → Toxic adenoma vs Graves' disease with incidental nodule vs Toxic MNG
- Investigation to differentiate → Thyroid scintigraphy (which was done — focal uptake = toxic adenoma) Answer: Toxic adenoma (focal hot nodule with normal/suppressed rest of gland)
Stem: 20-year-old woman with central neck swelling × 6 months, diffuse swelling moves with swallowing, tachycardia, resting tremor. Answer: B. Graves' disease — Young female, diffuse goitre (not nodular), thyrotoxic features. Not follicular CA (no malignant features described), not thyroglossal cyst (not midline upper neck), not thyroid cyst (diffuse, not nodular).
Stem: A 40-year-old lady has a central neck mass that moves with swallowing. Answer: F. Papillary thyroid carcinoma — In context of an EMQ about head and neck tumours, a central neck mass moving with swallowing in a 40-year-old female = thyroid origin. Among the options, PTC is the most common thyroid malignancy (most likely "tumour" answer in this EMQ context).
Stem: 80-year-old lady with enlarging neck swelling and dyspnoea × 6 months. Multinodular, cannot get below on right, tracheal deviation left. TFT normal. USG: bilateral isoechoic nodules (6 cm R, 4 cm L). FNAC: benign. CT: retrosternal extension right lobe. Key points tested:
- Management → Total thyroidectomy (symptomatic MNG with retrosternal extension, bilateral disease)
- Why total (not hemi) → Cannot get below mass = retrosternal extension; bilateral; compression symptoms
- Post-op complications → Haemorrhage, hypocalcaemia, RLN injury, hypothyroidism
Stem: Patient with 3 cm right neck hard mass moving with swallowing + multiple enlarged right lateral neck LNs. Paroxysms of headache, palpitations, sweating. CEA and calcitonin markedly raised. Answer: D. Medullary thyroid carcinoma — Calcitonin + CEA = MTC. Paroxysmal symptoms suggest concurrent phaeochromocytoma → MEN2A.
Stem: Patient with acute onset of 4 cm left thyroid swelling in 2 days, preceded by bouts of coughing. Answer: J. Thyroid haemorrhagic cyst — Acute onset over 2 days + triggered by coughing (Valsalva → haemorrhage into pre-existing cyst/nodule).
Stem: Patient with a small goitre, serum TSH and anti-TPO antibodies raised. Answer: C. Hashimoto thyroiditis — High TSH (hypothyroid) + raised anti-TPO = autoimmune thyroiditis.
Stem: 18-year-old lady with central neck swelling × 6 months, feels hot easily, disturbed menstrual cycle. Central neck diffusely enlarged, moves with swallowing. Answer: C. Thyroid nodule hyperplasia — Diffuse enlargement in a young woman with hyperthyroid symptoms. While this sounds like Graves', the answer options likely frame it as thyroid hyperplasia. (Note: if "Graves' disease" were an option, that would be preferred.)
Stem: A 45-year-old woman was found to have a clinical solitary thyroid nodule. What is the MOST LIKELY underlying pathology? Answer: A. Benign nodular goitre — 70% of all thyroid nodules, even clinically "solitary" ones.
Stem: 40-year-old woman with acute onset 3 cm right thyroid swelling within 2 days. Tracheal deviation to left. Difficulty swallowing.
- (a) 3 DDx: Haemorrhagic cyst (haemorrhage into thyroid cyst/nodule), thyroid malignancy (anaplastic or primary lymphoma), subacute thyroiditis
- (b) 2 Investigations: USG thyroid (characterize nodule, solid vs cystic, guide aspiration) + FNAC (cytology to exclude malignancy); also accept TFT
- (c) Treatment: Aspiration of cyst (if haemorrhagic cyst); or surgery if malignancy
- (d) Complication: Recurrence (if cyst); or surgical complications (haematoma, RLN injury, hypocalcaemia)
Stem: A 40-year-old lady has a central neck mass that moves with swallowing. Answer: F. Papillary thyroid carcinoma — Same EMQ as 2021. Thyroid-origin mass; PTC is the most common thyroid malignancy.
Stem: Woman had hyperthyroidism and large MNG, total thyroidectomy done with suction drain inserted. What is the purpose of the drain? Answer: D. To reduce haematoma formation by draining blood and serous fluid — The drain prevents haematoma accumulation which can compress the airway. Option B ("prevent airway obstruction by releasing pressure") is partially correct but the primary purpose is drainage of blood/fluid, not direct pressure release.
Trap
2025 MCQ Q53: Option B sounds attractive but the standard answer for "purpose of surgical drain" is to drain blood/serous fluid and thereby reduce haematoma formation. Airway protection is the consequence, not the mechanism. Always pick the most direct mechanism.
- GC 218 (Neck Mass): Thyroid nodule is the most common cause of an anterior neck mass that moves with swallowing. Always distinguish from thyroglossal cyst (midline, moves with tongue protrusion — tongue tug test positive) and lymphadenopathy (doesn't move with swallowing). [16]
- GC 063 (Thyrotoxicosis): When a thyroid nodule coexists with low TSH, always think toxic adenoma or toxic MNG → scintigraphy. [17]
- GC 216 (Dysphonia): Hoarseness with thyroid nodule = suspicious for RLN invasion by malignancy. Pre-op laryngoscopy mandatory. Post-op hoarseness = RLN injury complication. [18]
- Nuclear Medicine: I-123 or Tc-99m for functional assessment; I-131 for ablation therapy post-thyroidectomy. [19]
- Endocrine Interactive Tutorial: Post-thyroidectomy hypocalcaemia case — always monitor calcium post-op, check for Chvostek/Trousseau signs. [20]
High Yield Summary
MUST-KNOW for exam:
- Thyroid nodule prevalence depends on detection method (3–7% palpation vs > 30% USG/autopsy)
- Most common pathology = benign nodular goitre (70%)
- Investigation algorithm: TSH → USG → FNAC (Bethesda classification) → molecular testing for indeterminate
- Suspicious USG features: SHIT CME (Solid, Hypoechoic, Irregular margin, Taller-than-wide, Chaotic central vascularity, Microcalcifications, Extrathyroidal extension)
- Bethesda I/III → repeat FNAC; IV → lobectomy (FNAC cannot dx follicular CA); V → lobectomy + FS → TT; VI → TT
- Isotope scan: only if low TSH; hot nodules = no FNAC needed; cold = 10–20% malignancy risk
- Benign nodule surgery: hemi for solitary, total for MNG; non-surgical ablation (RFA etc.) for selected patients
- WDTC: total thyroidectomy ± RAI ± TSH suppressive T4; lobectomy acceptable for low-risk < 4 cm
- PTMC (< 1 cm): active observation is valid; near 100% survival
- MTC: calcitonin + CEA markers, total thyroidectomy + neck dissection, RET testing, MEN2 screening, prophylactic thyroidectomy in carriers
- Anaplastic: fatal, palliative, chemoirradiation ± debulking, median survival < 6 months
- Post-thyroidectomy complications: haemorrhage (emergency), hypocalcaemia, RLN injury, hypothyroidism
Active Recall - Thyroid Nodule & Cancer
[1] Lecture slides: GC 177. A thyroid nodule benign thyroid nodules; thyroid cancer.pdf [2] Past papers: 2024 Fourth Summative MCQ.pdf (Q59, Q66) [3] Senior notes: Ryan Ho Endocrine.pdf (Section 1.6 — Goitre and Thyroid Nodules) [4] Senior notes: Ryan Ho Endocrine.pdf (Section 1.6.2 — Other Thyroid Cancers) [5] Senior notes: MBBS Final MB (Surgery) (Felix PY Lai).pdf (Thyroid chapter) [6] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (Thyroid chapter) [7] Senior notes: Maksim Surgery Notes.pdf (p191–193) [8] Past papers: 2022 Fourth Summative Minicase.pdf (Case 2, Sections 3–4) [9] Past papers: 2025 Fourth Summative MCQ.pdf (Q24, Q53) [10] Past papers: 2021 Fourth Summative Assessment MCQ.pdf (Q9) [11] Past papers: 2023 Fourth Summative MCQ.pdf (Q4–Q8) [12] Past papers: 2018 Fourth Summative MCQ.pdf (Q12–Q13) [13] Past papers: 2019 Fourth Summative Mini Case.pdf (Case 2) [14] Past papers: 2020 Fourth Summative Assessment MCQ paper.pdf (Q58) [15] Past papers: 2024 Fourth Summative SAQ.pdf (Q9) [16] Lecture slides: GC 218. I have a swelling in the neck Neck mass.pdf [17] Lecture slides: GC 063. I am losing weight and sweating all the time.pdf [18] Lecture slides: GC 216. Dysphonia Laryngitis, voice abuse, tumour and laryngeal cancer.pdf [19] Lecture slides: hku nuclear medicine 2024_VM.pdf [20] Senior notes: Endocrine Interactive Tutorial.pdf (Case 1)
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