BRCA1 and breast carcinoma: In the largest study to date, the Breast Cancer Linkage Consortium (BCLC) reported that ER-negativity - defined by <1% of breast cancer cells expressing detectable ER by immunohistochemistry - conferred an age-adjusted odds ratio of 13.98 (95% confidence interval, 7.1 to 27.7; P < 0.0001) for BRCA1 mutation carrier status compared with controls unselected for family history (FH) [10].