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.

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

A concordant hyperfunctioning nodule is rarely malignant and is usually not biopsied. A non-functioning nodule is not diagnosed as cancer by the scan: its need for FNAC is determined by ultrasound pattern, size and clinical context. ^[22]

The lecture table uses an older Bethesda edition. The 2023 Bethesda System retains six categories but updates their average risk of malignancy and broadens management options. ^[21]

Key points:

• The 2023 system uses the single name AUS for category III rather than “AUS/FLUS”. ^[21]
• 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. Diagnostic lobectomy remains the definitive histological route when molecular testing or surveillance does not appropriately resolve management. ^[21]
• Category V/VI does not automatically mean total thyroidectomy. Initial extent of surgery is now risk-adapted; many unifocal intrathyroidal cancers ≤ 2 cm are managed with lobectomy. Routine frozen section has limited value for follicular-patterned lesions because invasion requires careful permanent-section sampling. ^[24]
• Core-needle biopsy is not routine first-line sampling, but it is not forbidden. It can be useful after failed/nondiagnostic FNA or when lymphoma, anaplastic carcinoma, metastasis or additional tissue for immunohistochemistry/molecular testing is suspected; it should be selected and performed by an experienced team. ^[29]

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

How to interpret it safely: “Rule-in” and “rule-out” are shorthand, not properties that travel unchanged between hospitals. PPV and NPV depend on the assay, the pre-test prevalence of cancer, ultrasound findings and whether NIFTP is counted as malignancy. Molecular testing should alter management only if its locally validated performance would change a shared decision; a “benign” classifier is not a lifetime guarantee, and an oncogenic result does not by itself dictate total thyroidectomy. ^[21][22]

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)

The slide's four scintigrams are a useful visual contrast: a cold defect interrupts otherwise uniform uptake; Graves' disease has diffuse bilateral uptake; a toxic adenoma is a single intense focus with suppression of the remaining gland; and toxic multinodular goitre gives a patchwork of multiple hot and cold areas.

PET/CT is not a routine first-line test for a thyroid nodule. However, focal incidental thyroid FDG uptake is clinically meaningful and should trigger dedicated ultrasound; whether to sample then depends on size and sonographic risk. PET/CT can also be used in selected advanced or radioiodine-refractory thyroid cancer. ^[22][24]

• 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]
• Laryngeal assessment: document the voice before thyroid surgery. Flexible laryngoscopy is particularly indicated for dysphonia, prior neck/upper mediastinal surgery, invasive/posterior disease or other concern for vocal-fold dysfunction; it is not automatically required for every uncomplicated benign nodule.
• Calcitonin: if medullary thyroid carcinoma suspected
• ESR, thyroid antibodies: if thyroiditis suspected

On the slide's lower image strip, the thoracic-inlet radiograph demonstrates how a goitre can deviate/narrow the tracheal air column, CT defines the retrosternal component and its relationship to trachea and great vessels, PET shows metabolically avid tissue but is nonspecific, and laryngoscopy directly tests vocal-fold position and mobility. These modalities answer different anatomical/functional questions; they are not interchangeable cancer tests.

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]

Why lobectomy for unilateral disease? It preserves the contralateral lobe's function, avoids the risks of bilateral surgery (bilateral RLN injury → airway compromise, hypoparathyroidism), and still provides histological diagnosis. It does not guarantee euthyroidism, so postoperative biochemical follow-up is required.

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]

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
• Benignity convincingly established (often two benign biopsies for non–very-low-suspicion nodules; requirements vary with sonographic pattern and local protocol)
• 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]

Reading the Ablation Images and Table

• Ethanol ablation chemically dehydrates/coagulates tissue and is best suited to recurrent cystic or predominantly cystic nodules.
• Radiofrequency, laser, microwave and HIFU cause thermal coagulation necrosis. The slide's RFA image shows a probe passed into the nodule under continuous ultrasound guidance; the HIFU image shows a focused extracorporeal beam without a needle track.
• Across the lecture table, expected volume reduction is roughly 50–80%, but it varies by technique, nodule composition and follow-up time. Voice change, pain, haematoma, skin burn, thyroid dysfunction and nodule rupture are technique-specific risks—not reasons to call the procedures risk-free.
• Current ATA guidance treats ablation as an alternative for carefully selected, convincingly benign, symptomatic/cosmetically troublesome nodules in centres with trained operators, a rescue plan and longitudinal ultrasound follow-up. Large nodules may require more than one session, and regrowth should prompt reassessment. ^[25]

For low-risk early-stage PTC (< 4 cm, no invasion, no LN metastasis): ^[1]

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]

2025 ATA guidance (simplified): ^[24]

• ≤ 2 cm, confined to one lobe, no ETE or clinical nodal/distant metastasis: lobectomy is the recommended operation when surgery is chosen; selected very small low-risk PTC may undergo active surveillance instead.
• > 2 to ≤ 4 cm with the same low-risk features: lobectomy or total thyroidectomy, based on tumour features, contralateral nodules and patient preference.
• > 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.

The neck diagram places the central compartment at level VI (prelaryngeal, pretracheal and paratracheal nodes) and the lateral compartments along levels II–V. A clinically involved compartment is treated by an anatomic, compartment-oriented dissection; isolated “berry-picking” of visible nodes is historical and inadequate. Prophylactic lateral dissection is not indicated. Prophylactic central dissection is not routine for small, non-invasive, clinically node-negative PTC; any possible staging benefit must be balanced against hypoparathyroidism and nerve injury. ^[24]

The slide reflects an older stage-based approach. Current RAI decisions are recurrence-risk- and response-adapted, not simply “stage I/II versus III/IV”. ^[24]

• Follows total/near-total thyroidectomy
• Preparation: thyroxine withdrawal vs recombinant TSH (Thyrogen)
• Adjuvant/therapeutic RAI: consider or recommend according to recurrence risk, residual iodine-avid disease, nodal burden and distant metastases
• Low-risk disease: RAI is not routine; lobectomy patients do not receive remnant ablation
• 30 mCi versus 100 mCi applies to selected remnant-ablation settings; it is not a universal equivalence for known persistent/metastatic disease
• 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)
• Do not suppress every patient indefinitely. The 2025 ATA guideline bases the TSH goal on the continually reassessed response to therapy: suppression below the reference range is suggested when biochemical or structural disease may persist, but it can be relaxed when an excellent response is achieved. Complete/undetectable TSH suppression is no longer recommended as a blanket target. ^[24]
• Balance any oncologic benefit against atrial fibrillation, bone loss and reduced quality of life.

• After total thyroidectomy ± RAI, Tg should be interpreted as a trend in context; very low or undetectable Tg is reassuring, but residual normal thyroid tissue, assay sensitivity and TSH level affect the result
• 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

Active observation criteria: ^[1]

• Biopsy-proven low-risk PTMC (incidental discovery is not required)
• No nodal/distant metastases, invasion or aggressive subtype; location must be suitable for safe observation
• 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

This slide is hypothesis-generating rather than a blanket standard of care. For an operable low-risk PTMC, the established de-escalation choices are active surveillance or surgery. Thermal ablation may be discussed only in carefully selected patients at experienced centres after confirming tumour location, absence of nodal/distant disease and the limitations of evidence and future pathology/surveillance. ^[24]