Challenges in the interpretation of peritoneal cytologic specimens

The presence of malignant cells in peritoneal washings leads to classification as International Federation of Gynecology and Obstetrics stage IC or higher in ovarian carcinomas and at least International Federation of Gynecology and Obstetrics stage IIIA in endometrial carcinomas. Unfortunately, the morphologic examination of cytologic specimens has not proven to be a sensitive or specific diagnostic tool. Malignant cells might be few in number and might be unrecognized among a large population of mesothelial cells and/or macrophages, or reactive mesothelial cells might be misinterpreted as neoplastic cells leading to unnecessary chemotherapy.

To evaluate the main pitfalls in the evaluation of peritoneal washings in patients with gynecologic malignancies and analyze the ancillary studies that might be helpful to achieve the correct diagnosis with an emphasis on immunocytochemistry.

A comprehensive review of the literature was performed.

Peritoneal effusions may represent major challenges to the pathologist and can have important clinical implications. Immunostains for epithelial markers such as B72.3, MOC-31, and Ber-EP4 represent the best available markers to identify epithelial cells. Caution is advised to not overdiagnose endometriosis or endosalpingiosis as adenocarcinoma.