BRCA1 and breast cancer: The majority of breast cancers diagnosed in women with a BRCA2 mutation are ER-positive.2,13 BRCA2 tumours are significantly more likely to be ER-positive compared to both BRCA1 tumours and sporadic tumours.13 We observed this in the current cohort, with 77% of the BRCA2 carriers having ER-positive tumours.