A 66-year-old male visited with constipation. Intra-pelvic cystic mass (332 cm
3
) was found, and PSA was 32.4 ng/ml. Biopsy of the prostate was performed. It wasn't adequate specimen for diagnosis, but the PSA of the fluid was 4791.0 ng/ml. RARP was performed. To make surgical field more visible, fine needle was stuck from the patient's perineum into the cyst intraoperatively. The patient was discharged with nothing complications. It was mucinous adenocarcinoma of the prostate, pT3b, RM1. The patient is now receiving ADT but no recurrence and metastasis are seen to date.