CLINICOPATHOLOGICAL FEATURES IN ENDOMETRIAL CARCINOMA WITH MISMATCH REPAIR DEFICIENCY AMONG CHINESE WOMEN YOUNGER THAN 50 YEARS OF AGE

Objective Mismatch repair (MMR) deficiency can lead to genome instability and closely correlated with carcinogenesis of endometrial carcinoma and mainly caused by MMR gene germline mutation known as Lynch syndrome (LS) or epigenetic mechanisms of MLH1 promoter methylationThe main objective of the present study is to correlate the clinicopathological features in endometrial carcinoma from 92 Chinese women younger than 50 years of age with the MMR status. Methods In total 92 cases of consecutive hysterectomy specimens with EC in patients younger than 50 years of age were analyzed. We performed immunohistochemistry staining for 4 MMR proteins,and two groups (MMR deficiency group and MMR normal group) were subdivided according to the outcome of immunohistochemistry staining.Results 38 cases (42%) with the negative expression of MMR proteins are selected for analysis of their clinical and pathological features. This group included 34 cases of endometrioid adenocarcinoma, one case of clear cell adenocarcinoma, three cases of the mixed types including clear cell, serous and neuroendocrine carcinoma mixed with classic endometrioid adenocarcinoma respectively. In addition to squamous differentiation, 29% cases also exhibit other differentiations including mucinous, clear cell, a lot of papillary structures, dedifferentiated, and secretory types. There are 10 cases showing features of peritumoral and tumor infiltrating lymphocytes. Seven cases have synchronous carcinoma of other sites besides the uterus. Conclusions The MMR deficient group showed more morphological differentiations including mucinous differentiation, frequent tumor infiltrating lymphocytes, and more frequent synchronous carcinomas of other sites than tumors with a normal immunophenotype of the MMR genes. Features of dedifferentiated EC originated in the lower uterine segment were not identified in our study. Endometrial carcinoma in Chinese patients younger than 50 years of age is more likely to be LS associated carcinoma.