Tumor and matched normal tissue samples were collected from 405 patients with five breast cancer subtypes: luminal A (<i>n</i> = 130), HER2-negative luminal B (<i>n</i> = 100), HER2-positive luminal B (<i>n</i> = 96), non-luminal HER2-positive (<i>n</i> = 36), and triple-negative breast cancer (TNBC, <i>n</i> = 43). This evidence concerns the gene ERBB2 and breast cancer.