In BRCA2 carriers, the ER-negative breast cancer PRS displayed a smaller per SD HR for breast cancer risk (HR = 1.15, 95% CI =  1.10 to 1.20, P = 6.8×10−10) compared with BRCA1 carriers, whereas the overall breast cancer PRS (HR = 1.22, 95% CI =  1.17 to 1.28, P = 7.2×10−20) and the ER-positive PRS (HR = 1.22, 95% CI = 1.16 to 1.27, P = 4.0×10−19) displayed stronger associations. Here, BRCA1 is linked to breast cancer.