Assessment of Histologic Prognostic Factors in Peritoneal Malignant Mesothelioma

Malignant peritoneal mesothelioma is a rare neoplasm. The most common type, the epithelioid type, has been further divided into histological patterns of tubulo-papillary, acinar, adenomatoid, micropapillary, or solid. Its prognosis is improved by the use of a locoregional treatment combining extensive cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC), which increases survival up to 50 months. Histology is one of the most important prognostic variable that, forms the basis for treatment decisions. However, the prognostic of the epithelioid type varies greatly due to its tumor heterogeneity. It is therefore necessary to find prognostic factors of malignant epithelioid peritoneal mesothelioma in order to better define the therapeutic strategy. Among histological factors, solid growth, tumor necrosis, nuclear atypia, and mitotic count were found to be independent prognostic factors in epithelioid malignant pleural mesothelioma. However, in epithelioid malignant peritoneal mesothelioma (EMPM), these factors were studied in small and heterogeneous series in terms of histological growth and definitions used for histological factors. The present large study was conducted to investigate the prognostic impact of several histologic factors in EMPM. Their prognosis impacts were assessed using overall survival (OS) and progression-free survival (PFS) in EMPM.