In addition to BRCA1 and BRCA2, germline mutations in five additional susceptibility genes, including tumour protein P53 (TP53), phosphatase and tensin homologue (PTEN), checkpoint kinase 2 (CHEK2), ataxia telangiectasia mutated (ATM), and partner and localizer of BRCA2 (PALB2), have been recognized as cancer‐related genes in breast cancer patients.41, 42, 43, 44. This evidence concerns the gene CHEK2 and breast cancer.