ATM and breast cancer: BC may be attributable to mutations in high-penetrance genes such as BRCA1, BRCA2, p53 and PTEN, as well as moderate or low penetrance genes (e.g., CHEK2, ATM, HRAS1, BRIP1, and PALB2), but these mutations account for a relatively small proportion of the heritable risk in these BC families [6], [7].