Signet-ring cell carcinoma of the prostate.

We report an intriguing case of signet-ring cell carcinoma of the prostate, ie, a rare histopathologic pattern of prostatic carcinoma. We present the results of histologic, immunohistologic, and electron microscopic examinations in our case, and we compare the findings with those of cases that have been previously reported. Although the histopathologic findings in the rare cases of signet-ring cell carcinoma of the prostate thus far reported have varied greatly, the following conclusions can be made: (1) signet-ring cell carcinoma of the prostate is a high-grade carcinoma; (2) a prostatic primary should be considered in cases of metastatic signet-ring cell carcinoma, especially when results of gastrointestinal studies are unelucidating; and (3) staining for mucin, lipid, prostate-specific antigen, prostate-specific acid phosphatase, and carcinoembryonic antigen is variable.