Benign cystic mesothelioma: unknown cause of abdominal mass

Abstract

Benign cystic mesothelioma (BCM) is a rare and benign disease that arises from the peritoneal mesothelium. It occurs predominantly in young to middle-aged women. The majority of cases were associated with a history of abdominal or pelvic operation, an endometriosis, and pelvic inflammatory disease. The etiopathogenesis is still unclear. Malignant transformation is extremely rare with only two cases reported in the literature. Like the etiology, the name of this entity is also controversial. Some authors prefer the term “peritoneal inclusion cyst” instead of “benign multicystic mesothelioma” and argue that the term mesothelioma should only be used when there is evidence of atypia. Most cases of BCM are discovered incidentally. Others reflect sequela of tumor mass effect. It appears intra-operatively as large, multi-focal, cystic lesions in the peritoneal and pelvic cavity. Diagnosis is achieved through surgical sampling with histopathological examination. Immunobiologically, BCM exhibits multiple small cystic spaces with flattened lining containing calretinin positive cells without atypical features, mitotic figures, or tissue invasion. Treatment includes cytoreductive surgery. We report on a 38-yearold woman who presented an abdominal mass discovered incidentally. Laparoscopic exploration revealed two cystic masses. The whole tumor was successfully excised and histopathology revealed benign cystic peritoneal mesothelioma.