Cytomorphologic characteristics of fine needle core biopsy of multicystic peritoneal mesothelioma: a case report and review of the literature.

Multicystic peritoneal mesothelioma (MPM) is an uncommon cystic mesothelial proliferative lesion. It occurs predominantly in women of reproductive age and most commonly arises in the pelvis. The preoperative diagnosis of MPM is difficult to establish based on clinical and radiographic findings, and has therefore traditionally been diagnosed following surgical resection. Due to differing management of MPM and its differential diagnoses including both benign and malignant lesions, it would be beneficial to diagnose MPM preoperatively. We report a case of MPM in a middle aged female that was diagnosed by fine needle core biopsy and touch preparations, allowing for appropriate clinical management. The cytomorphologic features of needle core biopsy, immunocytochemical studies and differential diagnosis are discussed. Furthermore, despite its infrequency, the current case emphasizes the importance of the inclusion of this entity in the differential diagnosis of cystic lesions of the abdomen and pelvis at the time of on-site evaluation and final diagnosis, in order to avoid misinterpretation of strips of benign mesothelial cells as inadequate for diagnosis.