Multicystic peritoneal mesothelioma A 28 year old female patient presented with pelvic and back pain for three years. Ultrasonographic examination revealed a multicystic mass located between bladder and uterus. With the clinical correlation, the tumor was evaluated as multicystic preitoneal mesothelioma macroscopically, histopathologically and by immunohisthemistry. In a review of the literature, differantial diagnosis of the tumor were discussed.