Within this group, MSI-H sporadic CRC (67%) is caused by epigenetic inactivation of the MLH1 gene whereas the remaining 33% is caused by germline mutations in MMR genes (particularly MLH1 and MSH2) leading to hereditary non-polyposis CRC (HNPCC) [21]. The gene discussed is MLH1; the disease is hereditary nonpolyposis colon cancer.