A 40-year-old woman with a solitary thyroid nodule has a markedly elevated serum calcitonin level. Total thyroidectomy confirms medullary thyroid carcinoma. Which additional serum marker, when elevated alongside calcitonin, correlates with tumor burden and is used in follow-up?
- A Carcinoembryonic antigen ✓
- B Thyroglobulin
- C Neuron-specific enolase
- D CA 19-9
Correct answer: A. Carcinoembryonic antigen
Explanation
Medullary thyroid carcinoma arises from parafollicular C cells and secretes calcitonin; these tumors also frequently express carcinoembryonic antigen, making serial CEA a standard adjunct for monitoring residual or recurrent disease. Thyroglobulin is the follow-up marker for papillary and follicular carcinomas arising from follicular epithelium, which kills option B. Neuron-specific enolase is used in neuroblastoma and small cell carcinoma, not medullary thyroid carcinoma.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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