MLH1 and hereditary nonpolyposis colon cancer: Interestingly, BRAF mutations are found only in MSI+ sporadic tumors that result from aberrant MLH1 promoter methylation and do not occur in MSI+ tumors from hereditary non-polyposis colorectal cancer (HNPCC) patients [5,8-10], thus providing a convenient discriminator between sporadic and familial cases.