Abstract
The biochemical activity of medullary thyroid carcinoma (MTC) includes production of calcitonin (CT), chromogranin A (CgA) and carcinoembryonic antigen (CEA). Routine CT measurement has been proposed as part of the initial evaluation of thyroid nodules and its use could ultimately decrease the morbidity and mortality of MTC. We report on a 43-year-old female patient with a large MTC expressing CT, CgA and CEA on immunostains but with negative preoperative CT and CgA results. Serum CEA was slightly increased and its rapid disappearance predicted radical cure by surgery as confirmed by 2-year follow-up. Our report illustrates that a diagnosis of MTC cannot always be excluded by negative preoperative CT. Fine-needle aspiration with cytomorphological analysis and complementary immunocytochemistry remains an essential diagnostic tool. Finally, serum aliquots must be stored before thyroid surgery in order to measure circulating forms of complementary markers found by tissue immunostaining (CEA and CgA)