A patient with medullary thyroid carcinoma has elevated serum calcitonin. Which additional tumor marker, if elevated, suggests co-existing pheochromocytoma in MEN 2A?
- A Urinary catecholamines and metanephrines ✓
- B CEA
- C CA 19-9
- D Serum PTH
Correct answer: A. Urinary catecholamines and metanephrines
Explanation
MEN 2A (Sipple syndrome) comprises medullary thyroid carcinoma, pheochromocytoma, and primary hyperparathyroidism. Pheochromocytoma is screened by measuring urinary catecholamines and metanephrines (or plasma free metanephrines). CEA can be elevated in medullary thyroid cancer but does not screen for pheochromocytoma; PTH elevation would indicate the parathyroid component.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
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