However, 3% of MMRd/MSI CRCs arise in the context of hereditary non-polyposis colorectal cancer (HNPCC), also known as Lynch Syndrome, which is a hereditary cancer syndrome characterized by heterozygous germline mutations occurring in MLH1, MSH2, MSH6, or PMS2 [81]. The gene discussed is MLH1; the disease is hereditary nonpolyposis colon cancer.