BRCA1 and breast cancer: Germline mutations in these 2 genes contribute to the pathogenesis of 20% to 40% of familial breast cancers in whites, thus accounting for 5% of all breast cancers.5 The risk of breast cancer in carriers of the BRCA1 and BRCA2 mutations is 51% to 75% and 33% to 54%, respectively, before age 70 years.