A 45-year-old woman undergoes thyroidectomy for a nodule. Histopathology shows nests of spindle-shaped cells in an amyloid stroma, and immunostaining is positive for calcitonin. Preoperative evaluation reveals a germline RET mutation. Before definitive surgery, which condition MUST be excluded?

• A Adrenal cortical adenoma
• B Primary hyperparathyroidism
• C Coexisting papillary carcinoma
• D Phaeochromocytoma ✓

Explanation

Medullary thyroid carcinoma with germline RET mutation signals MEN2, so phaeochromocytoma must be biochemically excluded with plasma or urinary metanephrines before any operation. An unrecognised phaeochromocytoma can precipitate a lethal catecholamine surge during anaesthesia and surgery. Hyperparathyroidism also belongs to MEN2D and should be screened, but it does not pose the same intraoperative mortality risk, which is why phaeochromocytoma is the mandatory exclusion. Amyloid stroma derived from calcitonin prohormone is the classic histological clue.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.