RT Journal Article SR Electronic T1 Malignant peritoneal mesothelioma in patients with endometriosis JF Journal of Clinical Pathology JO J Clin Pathol FD BMJ Publishing Group Ltd and Association of Clinical Pathologists SP 971 OP 974 DO 10.1136/jclinpath-2018-205099 VO 71 IS 11 A1 Kelly J Butnor A1 Justin Rueckert A1 Elizabeth N Pavlisko A1 Thomas A Sporn A1 Victor L Roggli YR 2018 UL http://jcp.bmj.com/content/71/11/971.abstract AB Aims Florid mesothelial hyperplasia is known to result from endometriosis. Well-differentiated papillary mesothelioma and multiloculated peritoneal inclusion cysts have also been described in women with endometriosis. To our knowledge, peritoneal diffuse malignant mesothelioma (MM) arising in the setting of endometriosis has not been reported. The purpose of this study is to report the clinicopathological characteristics of women with MM and endometriosis.Methods The surgical pathology files of a tertiary academic medical centre and the consultation files of one of the study authors were reviewed for cases of MM in females with and without endometriosis.Results Six women with MM and endometriosis ranging in age from 29 to 55 years (median=45 years) were identified. All had peritoneal MM and endometriosis involving the peritoneum and/or adnexa. Five had epithelioid MM and one had biphasic MM. Two had paraoccupational exposure to asbestos. The median age of women with MM and endometriosis (44.5 years) was significantly less than the median age of cases without endometriosis (58.0 years) (p value=0.01).Conclusions To our knowledge, this is the first report of MM in women with endometriosis. Interestingly, MM in the setting of endometriosis has only been observed in the peritoneum and not in other serosal cavities. The findings in the present study suggest that chronic serosal inflammation secondary to endometriosis may be an inducing factor in rare cases of MM of the peritoneum.