ERBB2 and breast cancer: The four main intrinsic heterogeneous molecular subtypes of breast cancer include luminal A, luminal B, human epidermal growth factor 2 positive (HER2)-enriched, and triple-negative breast cancer (TNBC)/basal-like [5,6,7]; of these, the human epidermal growth factor 2 positive (HER2+) and the triple-negative/basal breast cancer (TNBC/basal) subtypes are the most aggressive [9].