Well-differentiated papillary mesothelioma in association with endometrial carcinoma: a case report.

Background: Well-differentiated papillary mesothelioma (WDPM) is an uncommon tumor usually arising in the peritoneum and mostly an incidental finding during abdominal and pelvic surgery. Its natural history and association with other neoplasms is not clearly understood. We present a rare case of WDPM in association with high-grade endometrial carcinoma. To our knowledge, there are only two previously reported cases in the English literature of WDPM in association with endometrial carcinoma.
Case: A 62-year-old woman underwent pelvic surgery for a high-grade endometrial adenocarcinoma. At laparotomy an extensive peritoneal nodular fibrotic reaction was present, raising the clinical possibility of metastatic disease; however, intraoperative frozen section reported this as a mesothelial reaction. Cytologic examination of peritoneal washings revealed cohesive clusters of reactive-appearing mesothelial cells, some with papillary morphology, and no evidence of adenocarcinoma. The peritoneal biopsies showed no metastatic carcinoma. The endometrial tumor was an endometrioid adenocarcinoma.
Conclusion: The cytologic diagnosis of WDPM may be difficult because it is an uncommon entity and there are overlapping features with other neoplastic and nonneoplastic lesions of the female genital tract and peritoneum. Compounding this, WDPM may occur in association with other neoplasms. We highlight the potential for surgical and pathologic misinterpretation of this entity.