benign cystic mesothelioma a case series with one case complicated by pregnancy benign cystic mesothelioma bcm is a rare tumor of unknown origin most frequently encountered in women of reproductive age and with unknown etiology most patients have a history of previous pelvic operation endometriosis or pelvic inflammatory disease preoperative diagnosis is difficult we report the cases of three patients with one case complicated by pregnancy and discuss the diagnostic evaluation and treatment of this rare disease complete surgical resection is recommended if feasible however recurrent disease is not uncommon clinical positive effects of different adjuvant medical treatments are also discussed