Examining prospective data has revealed clinically relevant differences in carcinogenesis of mBC, especially the divergent prevalence of germline pathogenic variants (PVs) in the major BC susceptibility genes, BRCA1/2. PVs in BRCA2 represent the most frequent causative gene alteration and have been reported in about 10–16% of patients with mBC [4,7,8]. Here, BRCA1 is linked to breast cancer.