Specifically, one haplotype 35 kb upstream and in LD with NDN (rs850815 - rs850814 AA) was associated with a more aggressive breast cancer phenotype (Table 1): first, when tumors were classified on their PAM50 status [18], the AA haplotype was more frequent in poor prognosis basal-like tumors (frequency = 0.815 vs. 0.447 for all other subtypes; P = 1.99×10−6; FDR = 1.11×10−4); and second, the AA haplotype was more frequent in estrogen receptor (ER) negative compared to ER positive tumors (frequency = 0.716 vs. 0.459 for ER+; P = 3.57×10−4; FDR = 0.020). Here, ESR1 is linked to breast cancer.