The most significantly associated SNPs with Type 2 diabetes (rs7903146 and rs4506565) [22], [33] were also associated with breast cancer risk for BRCA1 mutation carriers in stage 1 and 2 analyses (p = 3.7×10−4 and p = 2.5×10−4 respectively); these SNPs were correlated with the most significant hit (rs11196174) for BRCA1 breast cancer (r2 = 0.40 and 0.37 based on stage 1 and 2 samples). Here, BRCA1 is linked to type 2 diabetes mellitus.