Endometriosis-associated ovarian tumors: morphological and immunohistochemical features

Background. In 2016, the World Health Organization published an updated version of the Histological Classification for ovarian tumors presenting a new category of endometriosis-associated tumors. The predictors of malignant transformation of endometriosis have not been clearly defined so far. Purpose. The search for histological and immunohistochemical markers of endometriosis-associated malignancy. Materials and methods. 28 female patients with endometrioid ovarian cancer and 11 patients with clear cell ovarian carcinoma were enrolled. Histological and immunohistochemical studies were carried out using conventional techniques. Immunohistochemistry was applied to determine the hormone receptor status: expression of steroid hormone receptors, BAF250a (ARID1A), PTEN, β-catenin, MSH6, PMS2, р-53, WT-1, proliferative index (Ki-67). Microsatellite instability (MSI) testing was conducted according to the standard protocol. Results. In all cases of ovarian cancer, histological examination showed one of the endometriosis features...