MSI-H/dMMR tumor are attributed as hereditary—arising from germline mutations in one of the four mismatch repair (MMR) genes (MLH1, MSH2, MSH6, PMS2) as part of the hereditary non-polyposis colorectal cancer (HNPCC) syndrome (2, 3)—or as sporadic, arising from globally hypermethylated colorectal cancer tumors featuring loss of gene expression of MLH1 due to promoter hypermethylation (4). This evidence concerns the gene MLH1 and colorectal cancer.