BRCA1 and BRCA2 mutations account for 4% of breast cancer cases and up to 24% of epithelial ovarian cancer cases, making these mutations the most common cause of hereditary breast and ovarian cancer syndrome. The estimated risk for breast cancer by the age of 70 is 45% to 85% (BRCA1 or 2) and, for ovarian cancer, 39% to 46% (BRCA1) or 10% to 27% (BRCA2). The prevalence of BRCA mutations is relatively high in certain populations (e.g., 1
in 40 among Ashkenazi Jews of European ancestry).