[A case of ductal adenocarcinoma of prostate associated with retroperitoneal multiple cysts].

A 61-year-old man came to our hospital with a complaint of lower abdominal pain. Computed tomography (CT) and magnetic resonance imaging (MRI) around his abdominal area showed large multiple cysts in the pelvis suggesting a malignant tumor. He showed high levels of serum carbohydrate antigen 19- 9 (CA19-9) and carcinoembryonic antigen (CEA). The complete diagnostic studies, including upper gastrointestinal endoscopy and colonoscopy examinations, failed to demonstrate the presence of alimentary primary tumors. With the diagnosis of cystic tumor in the pelvis, the operation was performed. The cysts adhered firmly to the surrounding organs including bladder and peritonium, which could not be resected completely. A histopathological diagnosis was papillary adenocarcinoma positive for prostate specific antigen (PSA). Because the level of serum PSA was 9.39 ng/ml, prostate biopsy was performed and ductal adenocarcinoma of prostate was revealed. After the operation, the levels of serum CA19-9 and CEA decreased to a normal level. Androgen deprivation therapy (ADT) was started, and the level of PSA was normalized one month later. Ductal adenocarcinoma forming cysts is rare. We reviewed 15 cases reported in the Japanese literature.