Primary carcinoid tumor of the prostate with concurrent adenocarcinoma: a case report.

Prostatic adenocarcinomas commonly exhibit neuroendocrine differentiation as demonstrated by immunohistochemistry. However, true carcinoids of the prostate are rare. We describe herein a case of a primary carcinoid occurring synchronously with a conventional adenocarcinoma in the prostate of a 66-year-old man. The carcinoid measured 0.2 x 0.2 cm and did not show contiguity with adjacent conventional, moderately differentiated adenocarcinoma. Immunohistochemical stains for chromogranin and neuron-specific enolase were strongly immunoreactive in the carcinoid but not in the adenocarcinoma. Both neoplasms demonstrated positive staining for prostatic acid phosphatase and prostate-specific antigen. Owing to the relatively minute size of the carcinoid, the possibility that this tumor will impact negatively on the patient's overall prognosis is not anticipated.