BRCA1 and breast cancer: Highest mutation rates were observed among patients with TN status (56.3%), especially among those with a positive family history of breast and/or ovarian cancer (69.2%) and patients with bilateral or second primary breast cancer (66.7%).30 In a subsequent larger study of 500 high-risk patients with breast cancer treated at our institution, approximately 13% of the whole group had pathogenic/likely pathogenic BRCA1/2 variants, and 8.8% had variants of uncertain significance.