MRC1 and hereditary nonpolyposis colon cancer: HNPCC, known as Lynch Syndrome, is an autosomal dominant genetic condition associated with germ-line mutations affecting one or several MMR genes (MSH2, MLH1, MSH6, PMS2, EPCAM) with consequent DNA mismatch repair (MMR) enzyme activity lost and increased genomic instability (microsatellite instability - MSI).