Hereditary breast cancers constitute about 5–10% of all BC cases but pathogenic variants in the high-risk (RR ≥ 4) breast cancer susceptibility genes BRCA1 [OMIM 113705] and BRCA2 [OMIM 600185] account for approximately 50% (0.7–29% BRCA1 and 1.5–25% BRCA2) of all hereditary breast cancers [4]. The gene discussed is BRCA1; the disease is breast cancer.