Previous studies have assessed whether SNP associations with breast cancer vary with ER status: rs2981582 (in FGFR2), rs3803662 in (TOX3), rs13387042 (in 2q35), and rs13281615 (in 8q24) were more strongly associated with ER-positive disease than ER-negative disease [9,10,27]. Here, ESR1 is linked to breast cancer.