Thyroid Carcinoma: Distinguishing Types
Thyroid malignancies are classified based on their cellular origin (follicular vs. parafollicular C cells) and prognosis. Understanding the histological clues is essential for board examinations.
1. Pathological Classification
| Type | Key Histological Findings |
|---|---|
| Papillary | Orphan Annie eye nuclei, psammoma bodies, and nuclear grooves. Most common. |
| Follicular | Uniform follicles; requires capsular/vascular invasion for diagnosis (cannot use FNA). |
| Medullary | Amyloid stroma (calcitonin); C-cell origin. Associated with MEN 2A/2B. |
| Anaplastic | Giant cells; highly undifferentiated, extremely poor prognosis. |
2. Exam Must-Knows
- Papillary Carcinoma: Excellent prognosis. Associated with radiation exposure in childhood.
- Follicular Carcinoma: Hematogenous spread is common (unlike Papillary, which spreads via lymphatics).
- Medullary Carcinoma: Part of MEN 2 syndromes (RET mutation). If you see elevated calcitonin, think Medullary.
- Anaplastic: Usually seen in elderly patients; presents as a rapidly enlarging neck mass that invades local structures.
Pathology Board Hint: For board exams, always memorize the buzzwords: Orphan Annie eyes = Papillary; Amyloid = Medullary; Capsular invasion required = Follicular.