The majority of individuals with Lynch syndrome possess at least one pathogenic germline mutation of the MMR genes MLH1, MSH2, MSH6 or PMS2. MLH1 and MSH2 genes are by far the most commonly mutated in Lynch syndrome patients accounting for ~70% of the mutations identified (32% in MLH1 and 38% in MSH2) [25,26]. This evidence concerns the gene PMS2 and Lynch syndrome.