Even including the estimated contributions of mutations in high penetrance (BRCA1/2, TP53, CDH1, LKB1, and PTEN), and moderate or low penetrance genes including SNPs associated with breast cancer identified through genome-wide association studies (GWAS), 50% of familial breast cancer predisposition still remains unexplained [6]. The gene discussed is BRCA1; the disease is breast carcinoma.