Some studies have suggested that the vast majority of multiple-case breast cancer families and families with breast and ovarian cancer would be caused by mutations in the BRCA1 or BRCA2 genes [5,7], but some analyses have suggested these initial studies may have overestimated the prevalence of BRCA1/BRCA2 mutations in hereditary breast cancer cases and mutations in these genes account for about 16% of the familial risk of breast cancer [8,9,10]. The gene discussed is BRCA1; the disease is breast cancer.