This intertumor heterogeneity is plausible in that breast cancer could originate from different cell types according to the tumor subtype[35] and is supported by previous studies showing the heterogeneous associations between SNPs and the prognosis of breast cancer by ER, PR and HER2 status[15,18–27], in agreement with the current study (Fig 2). This evidence concerns the gene ERBB2 and breast cancer.