OBJECTIVE To report clinical and pathologic findings of one case of mucin-producing urothelial-type adenocarcinoma of the prostate, and to discuss the diagnosis and prognosis of this disease.METHODS The patient was a 60-year-old man who had an 8-month history of urinary frequency and dysuria culminating in an aggravating condition for 10-days. Laboratory results were tPSA 3.0 and fPSA 0.4. An ultrasound and digital rectal exam showed no abnormal findings, so he was diagnosed as having benign prostatic hyperplasia, and underwent a transurethral prostate resection.RESULTS The findings during the operation resembled benign prostatic hyperplasia (BPH), whereas the pathological exam showed that the prostatic construction was deranged in the tumor infiltrating region, with many mucin lakes and signet ring cell in the cancer tissue. Immunohistochemical staining revealed that the cancer tissue was negative for prostate-specific antigen (PSA) and postive for carcinoembryonic antigen(CEA). Final diagnosis: mucin-producing urothelial-type adenocarcinoma of the prostate.After 50 Gy radiotherapy, the patient was free of recurrent signs and metastasis up to 8 months after operation.CONCLUSION Mucin-producing urothelial-type adenocarcinoma of the prostate is extremely rare. Its differential diagnosis mainly includes conventional prostatic adenocarcinoma with mucin production and secondary adenocarcinoma. The diagnosis and treatment of this disease should be further investigated.