PMS2 and hereditary nonpolyposis colon cancer: In contrast, the heritable forms of MSI-H CRCs, known as hereditary non polyposis colorectal cancers (HNPCC), harbor mutations in genes of the MMR-system, like MLH1, MSH2 (MUT-S homologue 2), MSH6 or PMS2 (post mitotic segregation 2).