Malignant Peritoneal Mesothelioma Associated With Endometriosis: A Clinicopathologic Study of 15 Cases.

Only a few cases of malignant peritoneal mesothelioma (MPeM) associated with endometriosis have been published; with chronic inflammation of the peritoneum associated with the latter being postulated as an inducing factor in the pathogenesis of this tumor. We assessed the clinicopathologic characteristics of MPeM associated with endometriosis to determine if there were other factors besides inflammation that may contribute to the pathogenesis in this patient population. Fifteen MPeM associated with endometriosis were retrieved from our files. Most presented with abdominal/pelvic pain, mass or distention; median age was 45 yr. Only 16% of patients had a history of asbestos exposure. In contrast, a third of the patients had a personal history of other neoplasms, and >80% had a family history of malignancies. Although most tumors had gross and microscopic features typical of MPeM, some had confounding features including "adhesion-like" appearance or gelatinous cysts/nodules, and signet ring cells. Tumors were epithelioid (9) and biphasic (6). MPeM was misdiagnosed as Müllerian carcinoma in 40% of cases. All patients (n=15) had cytoreductive surgery in addition to other therapies. Only 2/12 patients died of disease (17%). The 3- and 5-yr overall survival was 90%. MPeM associated with endometriosis tends to occur in patients with personal/familial history of malignancies, which may be a predisposing factor. In light of this finding, the role of endometriosis in the pathogenesis of MPeM is likely less relevant. The favorable outcome seen in these patients may be related to germline mutations or the hormonal milieu and needs further investigation.