Besides BRCA1/2 genes, pathogenic variants in other high- and moderate-risk genes, such as TP53, CHEK2, ATM, STK11, PALB2, among others, also lead to an increased breast cancer (BC) risk, revealing a high complexity in breast cancer predisposition (Elledge and Allred, 1998; Meijers-Heijboer et al., 2002; Walsh and King, 2007). The gene discussed is ATM; the disease is breast cancer.