Endometriosis-assEndometriosis-associated ovarian tumors: morphological and immunohistochemical features

Abstract

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, P-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. Atypical endometriosis was found in 39 % (11 / 28) of endometrioid tumors and in 9% (1/ 11) of clear cell carcinomas. Endometrioid ovarian cancer was found to be ER (74±7,8%) — and PR (67±5,4%) — positive; Ki-67 index was 68,2±3,7 %; loss of BAF250a (ARID1A) expression was observed in 14% (4/ 28), loss of PTEN expression in 29 % (8 / 28), nuclear expression of P-catenin in 32% (9/28) of cases. Loss of MMR expression was detected in 7% (2/28) of cases. MSI was found in one case only, which was also associated with loss of expression of BAF250a (ARID1A) and MSH6. Clear cell carcinoma of the ovary showed histological criteria for endometriosis; however, there were no changes immunohistochemical markers expression that were typical for endometriosis-associated malignancies. It could be due to a small number of patients in the group so further research is needed.Conclusion. Atypical endometriosis may be a morphological precursor of endometrioid and clear cell carcinoma of the ovary. Comprehensive assessment of a marker panel consisting of BAF250a (ARID1A), P-catenin, PTEN, p53, Ki-67 index, PMS2 and MSH6 will allow improving the diagnosis of atypical endometriosis and endometriosis-associated ovarian cancer.