ERBB2 and breast cancer: The molecular subclasses of breast cancer that are predictive of prognosis are based on their expression of specific genes including ER and HER2/neu: luminal-A subtype, ER+/HER2/neu-; luminal-B subtype, ER+/HER2/neu+; basal-like subtype, ER-/PR-/HER2/neu-; HER2/neu-overexpressing subtype, ER-/HER2/neu+ [1].