To prioritize the validation of novel potential driver genes based on the analysis of the HER2-negative components of HER2 heterogeneous breast cancers, we searched for genes i) whose expression is copy number regulated and are overexpressed when amplified, in a way akin to HER2 itself [2,3], and ii) that are recurrently amplified in the dataset of HER2 heterogeneous cases and/or preferentially amplified in HER2-negative tumors in the TCGA luminal breast cancer dataset. This evidence concerns the gene ERBB2 and breast cancer.