Primary signet-ring cell carcinoma of the prostate.

The occurrence of signet-ring cells within a mucinous prostatic carcinoma is an extremely rare finding. This cancer is characterized by both intracellular retention and extracellular secretion of mucinous material. We report a case of primary signet-ring cell carcinoma of the prostate that was confirmed by autopsy. The results of gross, microscopic, and immunohistochemical examinations are described.