Medullary thyroid carcinoma (MTC) arises from parafollicular C cells and secretes calcitonin. In familial MTC (MEN-2), the precursor lesion is:
- A Papillary microcarcinoma of the thyroid follicular cells
- B C-cell hyperplasia, which progresses to MTC ✓
- C Follicular adenoma undergoing malignant transformation
- D Hashimoto thyroiditis with focal C-cell neoplastic transformation
Correct answer: B. C-cell hyperplasia, which progresses to MTC
Explanation
In MEN-2A and MEN-2B (caused by activating RET proto-oncogene mutations), the histological precursor to medullary thyroid carcinoma is C-cell hyperplasia (neoplastic, not reactive), which progresses through multifocal MTC. C-cell hyperplasia involves proliferation of calcitonin-producing parafollicular cells within thyroid follicles and is bilateral. This progression from C-cell hyperplasia to MTC justifies prophylactic thyroidectomy in RET mutation carriers. Papillary and follicular carcinomas arise from follicular epithelial cells, not C cells.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
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Written and medically reviewed by the StethoPrep medical team.