A 48-year-old man with a medical history of hypertension and no family history of prostate cancer presented with abdominal distension, lower abdominal pain, and lower urinary symptoms. Physical examination revealed a palpable mass in the lower abdomen, and a digital rectal examination detected a firm mass on the anterior side of the rectum. Laboratory tests showed an elevated PSA level (7.9 ng/mL). Imaging studies indicated a solid mass connected to the prostate\'s posterior and rectum\'s anterior walls, along with bladder compression. Transperitoneal biopsy and histological analysis led to a diagnosis of a stromal tumor with uncertain potential malignancy. Considering the absence of apparent malignancy signs and the smooth outer wall of the tumor, the patient underwent, for the first time in the literature, a robot-assisted radical extraperitoneal prostatectomy for complete macroscopic resection. The surgery involved excision of the bulky pelvic mass, preservation of the urethra, and anatomical reconstruction. The postoperative course was uneventful, and we discharged the patient with no complications. The pathological examination documented the diagnosis of multilocular prostatic cystadenoma. Post-surgery follow-up examinations, including PSA levels and imaging scans, showed no signs of tumor recurrence. At the 3-, 6-, and 9-month follow-ups, the patient was asymptomatic and had fully recovered, with no urinary or sexual dysfunction reported.

Giant multilocular prostatic cystadenoma is a rare benign tumor that originates from the prostate gland. It usually is between the rectum and the bladder, and is composed of predominantly cystic enlarged prostatic glands in a fibrous stroma and spreads extensively in the pelvis. The mass usually causes a series of obstructive symptoms by compressing adjacent organs. Here we report a case of a giant multilocular prostatic cystadenoma in a 16-year-old patient, who is the youngest case reported up to now, complaining of difficulty in defecation.