We report a case of primary signet ring cell carcinoma of the prostate in a 75-year-old man. Serum prostate specific antigen (PSA) level at presentation was 9.3 ng/mL. The tumor was confined within the right prostate lobe and the patient was treated with neoadjuvant hormonal therapy and radical prostatectomy. He was alive with no evidence of disease 12 months after surgery. None of the tumor was stained with periodic acid-Schiff and Alcian blue. Immunohistochemically, the tumor was positive for PSA and prostatic acid phosphatase and negative for carcinoembryonic antigen. We reviewed 41 previously reported cases of signet ring cell carcinoma of the prostate, examining both histopathological and clinical information.

There have been no recurrence since transurethral resection in all IP in the study including the case recognized as aneuploid and positive for PCNA staining. But the present results suggest that among IPs, considered generally as a benign tumor, the case which has high proliferating character exists.

We confirmed the effects of this treatment. The prediction of effect of this treatment seemed to be indicative by fresh urinary cytologic examinations before instillation, especially cellular appearance and existence of large nuclear cells.