CHEK2 and breast cancer: Although CHEK2 founder mutations c.1100delC (p.Thr367Metfs∗15) and c.470T>C (p.Ile157Thr) have been shown to increase breast cancer risk by 2.6- and 1.4-fold, respectively,7,8,9 the extent to which the vast majority of CHEK2 variants are associated with elevated risk remains unclear.