Argyrophilic prostatic carcinoma. Case report with literature review on prostatic carcinoid and "carcinoid-like"...

An unusual prostatic neoplasm characterized by a carcinoid-like light microscopic pattern together with argyrophilia of tumor cells is described. Immunoperoxidase stain for prostatic specific antigen, however, was positive, indicating that this neoplasm was an argyrophilic prostatic carcinoma. Although the clinical significance of a carcinoid-like pattern and/or argyrophilia in prostatic carcinoma is currently unknown, pathologic recognition of these features is of paramount importance because prostatic carcinoma with these features has to be distinguished from true primary prostatic carcinoid tumor or, in areas of metastasis, from metastatic carcinoid originating from other sites such as the gastrointestinal or respiratory tracts. The value of the immunoperoxidase technique for prostatic specific antigen as well as prostatic acid phosphatase in this differentiation is stressed.