MLH1 and hereditary nonpolyposis colon cancer: Germline mutation in one of the DNA mismatch repair genes, MLH1, MSH2, MSH6, or PMS2 leads to hereditary nonpolyposis colorectal cancer (HNPCC), while MSI in sporadic colorectal cancer is predominantly due to hypermethylation of the MLH1 promoter and sometimes sporadic mutations [9].