Benign multicystic peritoneal mesothelioma - A rare differential diagnosis for cystic masses of the lower abdomen - Case report and review of the literature

Benign multicystic peritoneal mesotheliomas (BMPM) are rare tumors arising from the peritoneal mesothelium and most frequently encountered in women of reproductive age. Their pathogenesis is unclear and their neoplastic and reactive nature is still controversially discussed. While asbestos exposure is the main cause of malignant mesotheliomas, there is no known association of asbestos with BMPM. The biological behavior is characterized by a slow progress and high rate of recurrence after surgical resection. So far, approximately 140 cases have been reported. This lesion does not have a strong tendency to transform into malignancy with just two such cases reported in the literature to date. We present a case of a 30-year-old woman with an unclear multicystic mass in the lower abdomen with a largest diameter of 5.9 x 7.4 cm and elevated CA 125. Laparotomy was performed to rule out ovarian carcinoma. We additionally present a case of a 56-year-old woman with a suspicious cystic mass in the lower abdomen with a largest diameter of 5.7 x 2.2 cm. In this case laparoscopy was performed. The current literature on BMPM mostly consists of case reports; there is a lack of consistent definitions, and follow-up is mostly short. Although standard therapy recommendations do not exist, complete surgical resection is generally performed. Multimodal approaches that combine cytoreductive surgery and intraperitoneal chemotherapy as indicated for malignant mesotheliomas are not indicated. Although there is a high rate of recurrence after surgical resection, suggesting a "borderline character" of the tumor, the prognosis is excellent. Only one tumor-related death has been reported in the literature.