In the present study, among 100 cases of endometrial cancer, the frequency of MMR-deficient cases was 23 (23%) and the most common MMR-deficient cases were MLH1 / PMS2-deficient (4/23; 17.39%) and solitary MSH2-deficient (4/23; 17.39%). The gene discussed is MLH1; the disease is endometrial cancer.