This hereditary cancer syndrome is caused by the heterozygous germline inactivation of the DNA mismatch repair genes MLH1, MSH2, MSH6 and PMS2 (MutL homolog 1, melanocyte-stimulating hormone, postmeiotic segregation increased 2), which leads to microsatellite instability [17]. This evidence concerns the gene MLH1 and Inherited cancer-predisposing syndrome.