MRC1 and Lynch syndrome: Approximately 15% of CRCs display MSI due to either a germline mutation in MMR genes (genetic MSI, called Hereditary Non-Polyposis Colorectal Cancer or Lynch syndrome, 3%) or a somatic inactivation of one gene of the same group, most commonly through the hypermethylation of MLH1 promoter region (sporadic MSI, 12%) [76].