Mucin production in medullary carcinoma of the thyroid

Mucin production in medullary carcinoma of the thyroid is rarely mentioned in the literature. We studied 36 cases of medullary carcinoma; 32 lesions were sporadic and four were genetic variants. In 15 cases (42%), mucin production was demonstrated by histochemical means. In six cases (17%), the mucin was only extracellular; in three (8%), it was mostly extracellular, but with foci of intracellular deposits; and in six cases (17%), it was equally extracellular and intracellular. Mucin secretion could be demonstrated in both the primary thyroid tumor and the nodal metastases. No consistent correlation could be demonstrated between the histologic pattern, the staining properties of the tumor cells, and the sporadic or genetic occurrence of the tumor. Mucin was more frequently identified in medullary carcinomas (42%) than in other carcinomas (9.1%) of the thyroid gland. As mucin can be identified in approximately half of the medullary carcinomas, this primary thyroid lesion should be considered a possible source for a cervical node containing mucin positive carcinoma cells.