MLH1 and Leigh syndrome: Ren et al. (2020) identified 10 LS patients among 211 Chinese EC patients, with the most common mutation being MSH6 (70%), followed by MSH2 mutations (20%). In our study, 9 cases of LS were detected in 90 EC patients, including 3 MLH1, 2 PMS2, 2 MSH2, and 2 MSH6 germline mutations. Among the 9 LS patients, 7 were classified as MMRd and 2 as NSMP. The routine screening method involves IHC for MMR proteins and further MLH1 methylation testing for patients with MLH1 loss, followed by germline mutation testing based on the results.