BRCA1 and breast cancer: This is in contrast to breast cancer patients in the general population, for whom the proportion of ER-positive tumours is the lowest at young ages (in a group of 27,000 Danish patients, it was 57% under the age of 40) and increases with advancing age at diagnosis.13, 14 We have shown previously that BRCA2 patients have this paradoxical inverse relationship between ER-positive status and age, whereas BRCA1 patients follow the conventional pattern.14