Prostatic signet-ring cell carcinoma: case report and literature review.

Signet-ring cell carcinoma (SRCC) of the prostate is a very rare neoplasm and there have been only 38 cases reported to date. Here the 39th case of prostatic SRCC containing a small amount of neutral mucin, prostatic specific antigen (PSA) and prostatic specific acid phosphatase (PSAP) in the signet-ring cells is reported. It was also found that some intracytoplasmic lumina were derived from the shallow or deep invagination of luminal membranes of cancer cells that formed the neoplastic glands. Using immunohistochemistry, a combination of monoclonal antibodies against cytokeratins 7 and 20 as well as PSA and PSAP may be useful in differentiating prostatic primary SRCC from metastatic SRCC originating in the gastrointestinal tract.