Mucin-producing urothelial-type adenocarcinoma of the prostate as a mimicker of colonic adenocarcinoma: a case report and review of the literature.

A 59-year-old man presented with persistent urinary obstructive symptoms, gross hematuria, and mucusuria. Subsequently, a prostate-specific antigen (PSA)-negative mucin-producing urothelial type adenocarcinoma of prostate was found. The serum PSA level was within the normal limit. Colonoscopy, positron emission tomography, and other tumor surveys showed this to be the only prostate lesion. Microscopically, there was an adenocarcinoma with copious mucin production, with the formation of mucin pools. The neoplastic glands were variously arranged in cribriform, glandular, and villous adenoma-like patterns. This is a very rare tumor, of which there are only 20 cases reported in the literature in the English language. It is critical to distinguish it from mucinous acinar adenocarcinoma of the prostate and from metastatic adenocarcinoma of either the bladder or colon. This is mainly because mucin-producing urothelial type adenocarcinoma of the prostate has a different clinical behavior, and hence, the treatment plan is different from that for conventional prostatic adenocarcinoma. Specifically, it has a more aggressive clinical course and is unresponsive to hormone therapy.