ERBB2 and breast cancer: Therapy concepts of primary breast cancer and its distant metastases, including the brain metastases [6], consist of the local surgical and (neo-)adjuvant treatments (conventional chemotherapy, endocrine therapy, and radiation), as well as targeted therapy (anti-human epidermal growth factor receptor 2 (HER2)), which improve the patients’ survival and the chances for curability [4,7,8,9,10,11,12,13,14,15].