ERBB2 and breast cancer: Human epidermal growth factor receptor 2 (ERBB2, HER2)-positive BC, which constitutes about 15-20% of all BC cases (2), and its survival rate is low due to HER2 overexpression (immunohistochemistry [IHC] score of 3+ or IHC 2+ with a positive fluorescence in-situ hybridization [FISH] result), resulting in high recurrence and mortality rates (3).