Second, among all women in the cohort, 5.6% of patients carried a pathogenic variant in BRCA1, BRCA2, PALB2, or TP53. The high prevalence of inherited disease due to these high-penetrance genes makes a compelling argument for genetic testing for all breast cancer patients diagnosed before age 75 (the upper age threshold for participation in the CBCS). Here, BRCA1 is linked to breast cancer.