Immunohistochemical evaluation of microsatellite instability in endometrial cancers and its relationship with clinicopathological variables

Objective: Endometrial cancer is the most common invasive cancer of the female genital tract, accounting for 7% of all invasive cancers when we exclude skin cancers in women. In this study, we aimed to analyze the microsatellite instability of the hysterectomy materials, among those patient with endometrial cancer, by applying MLH-1, MSH-2, MSH-6 and PMS-2 antibodies which are MMR genes responsible for repairing DNA to tumour tissues via immunohistochemical method and their relationship with clinicopathologic features are investigated. Materials and Methods: Tumour materials of 140 patients who were diagnosed with endometrial cancer were included in the study of which were all total abdominal hysterectomy materials extracted between 2016 and 2021 in the Department of Medical Pathology of Zonguldak Bulent Ecevit University Faculty of Medicine. We chose to use the immunohistochemical evaluation of MMR genes in endometrial cancers, which is also the most cost-effective method for this study. Findings: After evaluating the tumour materials of 140 patients diagnosed with endometrial cancer, 103 (73,6%) were found to be microsatellite stable (MSS) and 37 (%26,4%) were found to be microsatellite instable (MSI). A significant statistical relationship was found between FIGO grade and the comparison between the MSI and MSS groups (p=0,03). A significant difference in the ratio of those were in the MSI group (48.6%), and the ratio of those were in the MSS group (29,1%), among the instances where myometrial invasion exceeds ½, suggested that this clinically significant difference was related to the MSI condition although there was no significant statistical relationship. Also we didn't find any statistical relationship between tumor-infiltrating lymphocytes (TILs) score and MSI and MSS status, however, in the group of where TILs score was 1 or more, the rate of MSI was greater. Conclusion: According to the findings in our study, there is a significant statistical relationship between the FIGO grade and MSI status (p=0,03). We found that results most likely are clinically significant, because of the association that we noticed between MSI with myometrial invasion and TILs score. In conclusion, we believe that using the most practical and easily accessible immunohistochemistry method to analyze the MMR gene expressions in those patients who were diagnosed with endometrial cancer, could become one of the current protocols for the diagnosis and treatment of the cancer and the post-operative management of the patients in gynecological oncology daily practice. Keywords: Endometrium, Microsatellite instability, MMR genes, TILs