Risks of breast cancer (BC), are known to be influenced by genetic susceptibility, with three general sources of information for assessing this susceptibility: (1) family history (FH); (2) high-risk but rather uncommon deleterious variants in several susceptibility genes, such as BRCA1 and BRCA2 (pathogenic variants, PVs); and most recently (3) common susceptibility variants, which can be efficiently combined into a polygenic risk score (PRS). The gene discussed is BRCA1; the disease is breast cancer.