MLH1 and Lynch syndrome: Approximately 90% of MLH1/PMS2 loss is due to somatic MLH1 promotor hypermethylation, and germline mutations in one of the mismatch repair genes, termed Lynch syndrome, accounts for approximately 10% of MMRd ECs and 3% of all ECs.23,24 Post et al. 24 also recently assessed the prognostic value of Lynch Syndrome within MMRd EC and found a trend towards improved recurrence free survival in patients with Lynch Syndrome compared with MLH1 hypermethylation.