Highlypenetrant, hereditary breast cancer genes include PTEN (Cowden'ssyndrome), TP53 (Li-Fraumeni syndrome), STK11(Peutz-Jeghers syndrome) and CDH1 (Hereditary diffuse gastric cancer.Germline mutations in CHEK2 gene are associated with a modest increasein the risk of breast (15-25% lifetime risk) and colorectal cancer in the hereditarybreast and colon cancer syndrome (HBCC) (Euhus andRobinson, 2013; Meijers-Heijboer etal., 2003). This evidence concerns the gene CHEK2 and breast cancer.