[Peritoneal cyst. A case report].

Cystic mesothelioma is a rare benign tumor of the abdominal and pelvic peritoneum, consisting of solitary or multiple cysts. No more than 130 cases are reported. Several risk factors such as chronic peritoneal irritation, caused by foreign bodies, infection or endometriosis, were hypothesized but the pathogenesis is still unknown. A 51-year menopausal woman was submitted to ultrasonography because of abnormal uterine bleeding. The scan revealed a right ovarian cyst (size 81 x 64 mm) with the feature of serous cyst. In the anamnesis a cystectomy of the right ovary and appendectomy were reported. At laparoscopy, then converted in laparotomy, a cyst arising from peritoneum of the posterior surface of the uterus was found. The right ovary was normal. The histopathological finding was: serous simple cyst of peritoneum. Ultrasonographic diagnosis was not confirmed by surgery; in fact, sometimes, it may be difficult to establish the origin of pelvic cystic mass, from ovary or peritoneum, by ultrasonography. It is mandatory to suggest a laparoscopy and/or laparotomy in case of pelvic cystic mass that does not regress in the time even after administration of oral contraceptives.