Abstract: Multilocular prostatic cystadenoma (MPC) is a rare benign tumor that originates from the prostate itself. MPC is usually characterized by large multilocular cysts located between the rectum and bladder. The clinical presentation includes obstructive voiding symptoms, such as poor stream, intermittency, sensation of incomplete emptying, acute urinary retention and sometimes constipation symptoms due to mechanical compression of the lower intestine. Most of the previously reported patients with MPC underwent open surgery. Although the natural history of MPC remains unknown, surgical excision may not always be necessary. Here we report the case of a 49-year-old male, treated by transurethral electroresection of prostate (TURP) for prostate cyst one and half years before．His biopsy of TURP showed benign prostatic tissue with no evidence of malignancy. However, the symptoms of urinary tract obstruction were obviously aggravated after the operation. Acute urinary retention occurred intermittently 3 times. In our hospital, his total prostate specific antigen (tPSA）was 5.440 μg/L，free prostate specific antigen (fPSA ) was 1.528 μg/L. After examination, it was considered as benign lesions clearly. In the operation of TURP, we found that the tumor was multilocular cystic. Histologically，the cell was mucus. Concerning the immunophenotype，CK5/6(+）， p40（+）， PSA（+）， P504S（+）， PAX2（-）， PAX8（-）， MUC1（+）， MUC5ac（+）, the results of special staining were as follows: AB（+）， PAS（+）．At the end of the follow up 3 months later, the routine semen analysis results showed that his semen volume was 3 mL and the sperm density and sperm mobility were normal. At the end of the follow up eight months later, the patient remained free of lower urinary tract symptoms and there were no signs of recurrence. His international prostate symptom score (I-PSS) had dropped from 32 to 4, and quality of life score (QOL) had dropped from 6 to 2. MPC is a rare benign tumor originating from the prostate. TURP may aggravate the symptoms of lower urinary tract obstruction in patients with MPC, and may be temporarily observed for some asymptomatic young and middle-aged patients.

Key words: Cystadenoma, Prostate, Multilocular