A 50-year-old man with MEN2B has medullary thyroid carcinoma (MTC). MTC arises from which thyroid cell type and secretes which marker?

• A C cells (parafollicular cells); calcitonin ✓
• B Follicular cells; thyroglobulin
• C Hurthle cells; thyroid peroxidase
• D Lymphocytes; CD20

Explanation

Medullary thyroid carcinoma (MTC) arises from parafollicular C cells of neural crest origin, which normally secrete calcitonin. MTC characteristically shows amyloid stroma (amyloid derived from calcitonin precursors) and demonstrates calcitonin and CEA immunopositivity, both of which serve as tumour markers for diagnosis and surveillance. MTC is associated with RET proto-oncogene mutations — sporadic, MEN2A (ret + parathyroid + phaeochromocytoma), and MEN2B (ret + marfanoid + mucosal neuromas). Thyroglobulin is the marker for follicular and papillary thyroid carcinoma.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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