Primary prostatic carcinoid tumor with intracytoplasmic prostatic acid phosphatase and prostate-specific antigen.

A case of prostatic carcinoid tumor with lymph node metastases is reported. The patient was a 78-year-old male who died in ventricular fibrillation. At autopsy, a 2 X 2 cm, white, irregular tumor was found in the prostate and there were several enlarged para-aortic lymph nodes. Both specimens contained a characteristic carcinoid tumor. Argyrophil stains revealed strong positivity in the primary as well as in the metastatic tumors. Electron micrographs prepared from formalin-fixed tissue demonstrated numerous membrane-bound dense-core granules. Immunoperoxidase-labeled antibodies against both prostatic acid phosphatase and prostate-specific antigen localized in the tumor cells. The ultrastructural and immunohistochemical results support differentiation of the tumor cells toward both prostatic epithelial cells and endocrine cells. We believe that this is the first reported case of a prostatic carcinoid tumor in which specific prostatic tissue markers have been demonstrated in the tumor cells.