Endocrine Abstracts

Introduction: The diagnostic accuracy of fine needle aspiration (FNA) in case of medullary thyroid cancer (MTC) has been less studied than in other thyroid cancers. The complementary measurement of calcitonin in the needle washout fluid after FNA (FNA-Ct) could improve the usefulness of this technique.

Materials and Methods: Description of two cases of patients with thyroid nodules suspicious for MTC in whom FNA-Ct was measured as a complementary diagnostic method.

Results: CASE 1: a 53-year-old man who was referred to our Endocrinology department due to a 1.3 cm right thyroid nodule and a 6 cm left thyroid nodule, with elevated CEA in laboratory tests (11.7 ng/ml). The additional blood calcitonin measurement was also elevated (91.3 pg/ml). FNA was performed on both nodules as well as FNA-Ct measurement. The cytology of the right nodule was categorized as Bethesda III with undetectable FNA-Ct and that of the left nodule was Bethesda V with FNA-Ct of 240 pg/ml (2.6 times more elevated than in blood). Total thyroidectomy with central lymphadenectomy was performed and the histological result was MTC in the left nodule and follicular variant of papillary carcinoma in the right nodule. CASE 2: a 79-year-old woman with a history of rectal adenocarcinoma and chronic kidney disease stage IV who presented a progressive elevation of CEA in laboratory tests, hypermetabolic uptake in the left thyroid lobe on FDG-PET, that corresponded to 1.2 cm nodule. The blood calcitonin measurement was also elevated (332 pg/ml). FNA was performed and the cytological result was categorized as Bethesda III. However, FNA-Ct was 800,000 pg/ml (2409 times more elevated than in blood). Total thyroidectomy with central lymphadenectomy was performed, confirming the diagnosis of MTC in the left nodule.

Conclusions: Although there are no obvious cut-off points, the FNA-Ct measurement showed values in both cases higher than blood levels, reinforcing the diagnostic suspicion of MTC and helping to decide on a more appropriate surgical approach. In neither case had cytology been reported as suggestive of CMT.