ERBB2 and breast cancer: According to the expression of molecular markers of estrogen or progesterone receptors and human epidermal growth factor receptor 2 (HER2), breast cancers are divided into three major subtypes, including hormone receptor positive/HER2 negative subtype (70%), HER2 positive subtype (15%-20%) and triple-negative subtype (tumors lacking all 3 standard molecular markers,15%) (2).