Calcitonin and histaminase in C-cell hyperplasia and medullary thyroid carcinoma. A light microscopic and immunohistochemical study.

The thyroid glands of 13 patients with gross medullary thyroid carcinoma (4 sporadic, 9 familial), 3 patients with clinically occult microscopic carcinoma, and 5 patients with C-cell hyperplasia have been studied using routine light microscopy and immunohistochemical techniques. The morphologic features of the spectrum of C-cell proliferative lesions are reviewed, and the distribution of calcitonin and histaminase in these lesions is compared. Calcitonin production is a property of normal, hyperplastic, and neoplastic C cells, and the hormone is present in the majority of tumor cells in medullary carcinoma. In contrast, histaminase is shown to be present only in some cells in medullary carcinoma and not in normal or hyperplastic C cells. We believe that the presence of histaminase in a C-cell proliferative lesion is an atypical phenomenon and indicative of malignancy.