Cytological aspects of melanotic variant of medullary thyroid carcinoma

We had the opportunity to examine a case of fine-needle aspiration (FNA) of a melanotic variant of medullary thyroid carcinoma (MTC) in a 20-yr-old ma n. The patient presented a single node, hardened and mobile upon deglutitio n, in the right lobe of the thyroid, for 9 mo, without symptoms of glandula r dysfunction. Calcitonin (138 pg/ml), urinary calcium (177 mg/dl), and the carcinoembryonic antigen (341 ng/ml) were increased The nodular aspirate, drawn by FNA, was represented by pleomorphic cells, with frequent intranucl ear cytoplasmic inclusions, sometimes bi- or multinucleated with abundant, finely granular cytoplasm, sometimes containing a brown pigment resembling melanin. An immunohistochemical study using monoclonal antibodies (Dako Cor p., Carpinteria, CA) showed that the neoplastic cells were intensely and di ffusely positive for calcitonin and chromogranin, and focally positive for HMB45. In view of these findings, the case was characterized as a melanotic variant of medullary carcinoma, a rare type of neoplasia, but having a pro gnosis similar to the classical variant of MTC. (C) 2001 Wiley-Liss, Inc.