Breast cancer (BC) is the second most common cause of cancer-associated death in women [1], even though, the prognosis considerably varies for hormone receptor (HR+), human epidermal growth factor receptor 2 (HER2+; with or without HR expression) and HER2-/HR- diseases, the latter classified as triple-negative breast cancer (TNBC). This evidence concerns the gene ERBB2 and breast cancer.