Calcitonin-secreting carcinomas of the prostate. An immunohistochemical and ultrastructural analysis.

Two cases of calcitonin-producing carcinomas of the prostate are reported. Light microscopical, immunohistochemical, and ultrastructural investigations have been performed. These tumors displayed a remarkable dual, endocrine and common epithelial (exocrine), differentiation. However, they presented two different architectural growth patterns. Of particular interest, numerous calcitonin cells were immunocharacterized. In addition, the endocrine component could harbour carcinoembryonic antigen, serotonin, human chorionic gonadotrophin, and prostate-specific acid phosphatase immunoreactive cells. Ultrastructural analysis confirmed the presence of numerous endocrine cells. These findings are not unexpected, since calcitonin, serotonin, and human chorionic gonadotrophin immunoreactive cells are normal and constitutive inhabitants of prostate gland. In the current cases, calcitonin cells showed a strong carcinoembryonic antigen immunoreactivity, as observed also in thyroidal C-cells. This peculiar kind of prostatic carcinoma might be compared to certain thyroidal tumors of intermediate type coupling parafollicular and follicular differentiation.