Some evidence has suggested that breast-feeding may reduce breast cancer risk even among women at highest risk of breast cancer, specifically BRCA1 mutation carriers (Jernstrom et al. 2004; Kotsopoulos et al. 2012), who tend to develop ER-negative tumors (Foulkes et al. 2004) and have elevated CBC risk (Graeser et al. 2009; Malone et al. 2010). This evidence concerns the gene BRCA1 and breast cancer.