Multiple endocrine neoplasia type 2A (MEN2A) is associated with RET proto-oncogene mutations causing medullary thyroid carcinoma, phaeochromocytoma, and parathyroid hyperplasia. In MEN2A-associated medullary thyroid carcinoma, what is the staining characteristic that confirms calcitonin-secreting C-cell origin?
- A Positive mucin staining with Alcian blue
- B Positive amyloid (Congo red) staining of the stroma due to calcitonin-derived amyloid deposits ✓
- C Positive periodic acid-Schiff (PAS) staining of cytoplasmic glycogen
- D Positive Sudan III staining for intracytoplasmic lipid droplets
Explanation
Medullary thyroid carcinoma (MTC) arises from parafollicular C-cells which secrete calcitonin. A characteristic histological feature of MTC is the amyloid-rich fibrous stroma, which stains positive with Congo red and shows apple-green birefringence under polarised light. This stromal amyloid is derived from calcitonin precursor peptides (procalcitonin) secreted by the tumour cells, which misfold into amyloid fibrils — the same mechanism as other peptide-hormone-derived amyloids. Positive calcitonin immunostaining confirms C-cell origin. Elevated serum calcitonin is the tumour marker for MTC screening in RET mutation carriers.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.