Thyroid Nodules

Basics & Presentation - Neck's Lumpy Riddles

• Definition: Discrete thyroid lesion, radiologically distinct from parenchyma.
• Prevalence: Common; ↑ age, female, iodine deficiency, radiation exposure. Palpable 4-7%, ultrasound 50-70%.
• Etiology:
  • Benign (>90%): Colloid nodules, adenomas, cysts, Hashimoto's thyroiditis.
  • Malignant (<10%): PTC (commonest), FTC, MTC, anaplastic, lymphoma.
• Clinical Features:

  ⭐ Most thyroid nodules are asymptomatic and benign, discovered incidentally.

  • Painless neck mass (most common).
  • Compressive symptoms (if large): Dysphagia, dyspnea, hoarseness (RLN involvement).
  • Functional nodule (rare): Symptoms of thyrotoxicosis.
  • Pain (uncommon): Suggests hemorrhage into cyst or thyroiditis.
  • Red flags for malignancy: Rapid growth, firm/hard, fixed, vocal cord palsy, cervical lymphadenopathy, age <20 or >60. oka

Imaging & Labs - Scan & Scope Secrets

• Initial Labs:

  • TSH: Best initial test.
  • If TSH ↓: Thyroid Scintigraphy ($^{123}$I or $^{99m}$Tc).
  • If TSH normal/↑: Proceed to USG.
  • Serum Calcitonin: If Medullary Thyroid Carcinoma (MTC) suspected (e.g., family hx, MEN2).

• Ultrasound (USG) Neck:

  • Primary imaging for all palpable/incidental nodules.
  • Key for risk stratification (TIRADS).
  • High-risk features: Solid, hypoechoic, microcalcifications, irregular margins, taller-than-wide, extrathyroidal extension, suspicious lymph nodes.

• Thyroid Scintigraphy:

  • Indicated for low TSH nodules.
  • Hot nodule (hyperfunctioning): ↓ malignancy risk.
  • Cold nodule (hypofunctioning): ↑ malignancy risk (5-15%).

⭐ A suppressed TSH suggests a hyperfunctioning ("hot") nodule, which is rarely malignant; further evaluation with thyroid scintigraphy is indicated.

FNA & Bethesda - Bethesda & Beyond

• FNA (Fine Needle Aspiration): Key diagnostic tool for thyroid nodules, ideally USG-guided for accuracy.
• The Bethesda System (TBSRTC): Standardizes thyroid cytology reporting globally, crucial for guiding subsequent management decisions.

Bethesda Categories, Risk of Malignancy (ROM) & Management:

• I: ND/US (Non-Diagnostic/Unsatisfactory)
  • ROM: 5-10%
  • Mgmt: Repeat FNA, preferably USG-guided.
• II: Benign
  • ROM: 0-3%
  • Mgmt: Clinical and USG follow-up.
• III: AUS/FLUS (Atypia/Follicular Lesion of Undetermined Significance)
  • ROM: 10-30%
  • Mgmt: Options include Repeat FNA, molecular markers, or diagnostic surgery (lobectomy).
• IV: FN/SFN (Follicular Neoplasm/Suspicious for FN)
  • ROM: 25-40%
  • Mgmt: Diagnostic lobectomy; molecular markers can aid risk stratification.
• V: SM (Suspicious for Malignancy)
  • ROM: 45-75%
  • Mgmt: Surgical intervention: (Near)Total Thyroidectomy or Lobectomy.
• VI: Malignant
  • ROM: 97-99%
  • Mgmt: Therapeutic surgery: (Near)Total Thyroidectomy; lobectomy for select low-risk cancers.

⭐ Bethesda VI (Malignant) has a 97-99% risk of malignancy, typically requiring surgical intervention.

Management Flow based on Bethesda:

Management Algorithms - Surgical & Other Sorties

• Benign (II): Observe; Rpt USG/FNA if ↑size/symptoms. Surgery if compressive/cosmetic.
• Indeterminate (III, IV, V):
  • AUS/FLUS (III): Rpt FNA, molecular markers, diagnostic lobectomy.
  • SFN/HCN (IV): Diagnostic lobectomy.
  • Susp. Malignancy (V): (Near) Total thyroidectomy or diagnostic lobectomy.
• Malignant (VI):
  • DTC (PTC/FTC):
    • MicroCa (<1cm, low-risk): Lobectomy.
    • Else: Total thyroidectomy + CND. Lateral ND if nodes+.
  • Medullary Ca: Total thyroidectomy + CND.
  • Anaplastic Ca: Palliative (surgery, EBRT, chemo).
• Post-op DTC: RAI ablation (high-risk), TSH suppression.

⭐ Papillary Thyroid Carcinoma (PTC) is the most common thyroid malignancy and often has an excellent prognosis with appropriate treatment.

High‑Yield Points - ⚡ Biggest Takeaways

• FNAC is the cornerstone for thyroid nodule evaluation.
• Most nodules are benign; papillary carcinoma is the commonest malignancy.
• The Bethesda system for FNAC reporting guides management.
• "Cold" nodules on thyroid scan are more suspicious for malignancy.
• Key malignancy risk factors: radiation history, rapid growth, hard/fixed nodule, lymphadenopathy.
• Initial test: TSH. If TSH is normal/high, FNAC is next.
• Solitary nodules often warrant more concern than multiple nodules in a goiter.