CHEK2 and hereditary nonpolyposis colon cancer: The mismatch repair (MMR) genes MLH1, MSH2, MSH6, and PMS2 are associated with hereditary nonpolyposis colorectal cancer (HNPCC)20 and APC mutations are found in individuals with familial adenomatous polyposis (FAP).21 Mutations in TP53, PTEN, CDH1, CHEK2, ATM, RAD51D, PALB2, and FANCM have been associated with increased risk of breast cancer22,23 or prostate cancer,19 although with varying penetrance.