ESR1 and breast cancer: Further, in our sample the proportion of the ER+ subtype among all BC cases of BRCA1 PV carriers in the ED group was 29.4% (20/68) and 55.6% (5/9) in the LD group, with missing data of receptor status for 52 tumors (ED: 48, LD: 4), whereas Mavaddat et al. reported in agreement with previous findings by Foulkes et al. an ER+ proportion of <20% among BC diagnoses before age 40 years, and of approximately 45% and >50% among BC diagnoses between ages 60 and 69 years, and >70 years, respectively [6, 7].