Results: The cumulative risk for breast cancer at 45 years in carriers of frequent path_BRCA1 variants was 20% (94% confidence interval 10–30%), compared to 35% (95% confidence interval 22–48%) in carriers of infrequent path_BRCA1 variants (p = 0.02), and to the 35% (confidence interval 32–39%) average for path_BRCA1 carriers reported by others (p = 0.0001). Here, BRCA1 is linked to breast cancer.