ERBB2 and neoplasm: Molecularly, BC is differentiated into luminal A, luminal B, HER2-enriched and triple-negative subtypes depending on positivity for estrogen receptors (ERs), progesterone receptors (PRs), the overexpression of human epidermal growth factor receptor 2 (HER2) and the tumor proliferation index level [8,9,10,11,12].