Thyroid Cancer

Thyroid Cancer - Thyroid 101: Risky Business

• Definition: Malignant tumor originating from thyroid follicular or parafollicular C cells.
• Epidemiology:

  • ⭐ Most common endocrine malignancy.

  • India: Accounts for ~1-2% of all cancers; incidence rising.
• Key Risk Factors:
  • Radiation exposure: Especially in childhood (< 15 yrs); dose-dependent (e.g., 5-10 Gy).
  • Family history: Syndromic (e.g., MEN2, FAP, Cowden syndrome) or non-syndromic familial thyroid cancer.
  • Iodine status: Deficiency (↑ follicular cancer risk); Excess (possible ↑ papillary cancer risk, debated).
  • Female gender.
  • Age extremes (childhood, >45 yrs).
  • Pre-existing benign thyroid conditions (e.g., goiter, adenomas).

Thyroid Cancer - Cellular Rogues Gallery

• Thyroid malignancies: follicular epithelial or parafollicular C-cell origin.
• 📌 Papillary: Popular (~80%), Psammoma bodies, Positive Prognosis.

Thyroid Cancer - Nodule CSI: Case Cracked

• Presentation: Solitary thyroid nodule (most common); hoarseness, dysphagia, stridor (compressive symptoms).
• Diagnostic Workup:
  • USG: Initial. Suspicious: microcalcifications, hypoechogenicity, irregular margins, taller-than-wide, ↑vascularity.
  • Serum TSH: If normal/high & USG suspicious → FNAC. If low → Radionuclide scan (cold nodule? → FNAC).
  • FNAC: Bethesda System (Categories I-Nondiagnostic to VI-Malignant).
  • Serum Calcitonin: If Medullary Thyroid Cancer (MTC) suspected (family Hx, USG).
  • Serum Thyroglobulin (Tg): Post-op surveillance for differentiated cancers (PTC, FTC).

⭐ FNAC is the most important initial diagnostic test for a thyroid nodule.

Thyroid Cancer - Thyroid Takedown Tactics

• Surgery: Primary treatment.
  • Total Thyroidectomy (TT): Standard for most.
  • Lobectomy: For small, low-risk unifocal DTC.
  • Neck Dissection: Nodal disease (therapeutic); prophylactic central for MTC.
• Radioactive Iodine ($I^{131}$): Post-TT for DTC remnant/mets.
  • Ablation (30-100 mCi), adjuvant, metastatic disease.
• TSH Suppression: Levothyroxine to ↓TSH, prevent recurrence.
  • High-risk: <0.1 mIU/L. Low-risk: 0.1-0.5 mIU/L.
• Advanced/Refractory:
  • EBRT: Unresectable, residual disease, palliative.
  • Systemic: TKIs (Lenvatinib-DTC, Vandetanib-MTC), Chemo (ATC).

⭐ Differentiated thyroid cancers (papillary, follicular) are typically iodine-avid, making $I^{131}$ therapy effective.

Thyroid Cancer - Post-Op: The Long Haul

• Prognostic Factors: Age (e.g., <55 yrs better), tumor size, extrathyroidal extension, histological type, molecular markers (e.g., BRAF).
• Differentiated Thyroid Cancer (DTC) Follow-up:
  • Serum Thyroglobulin (Tg) & anti-Tg antibodies (key for recurrence).
  • Neck Ultrasound (USG).
• Medullary Thyroid Cancer (MTC) Follow-up:
  • Serum Calcitonin & CEA levels.
  • Neck USG.

⭐ Rising Thyroglobulin (Tg) levels post-thyroidectomy in DTC strongly suggest recurrence or persistent disease.

High‑Yield Points - ⚡ Biggest Takeaways

• Papillary Ca: Most common, Orphan Annie eyes, psammoma bodies, lymphatic spread, best prognosis.
• Follicular Ca: Hematogenous spread, needs capsular/vascular invasion for diagnosis (not by FNAC alone).
• Medullary Ca: From C-cells, linked to MEN2 (RET), secretes calcitonin (tumor marker).
• Anaplastic Ca: Elderly, rapid growth, aggressive, worst prognosis.
• FNAC: Best initial test for thyroid nodules.
• Treatment: Total thyroidectomy then RAI ablation for differentiated (Papillary, Follicular) cancers.