MSH2 and hereditary nonpolyposis colon cancer: Overall, screening for sequence variants in HNPCC related genes allowed the detection of 56 different substitutions with a definite or potential pathogenic significance in 72 patients, including 26 in MLH1 (46.5%), 28 in MSH2 (50%) and 2 in MSH6 (3.5%) (Table 1 and Table S5).