ERBB2 and breast cancer: For example, adjuvant chemotherapy with trastuzumab is highlighted in the National Comprehensive Cancer Center (NCCN) guidelines for the treatment of HER2-positive breast cancer [1], while the European Society for Medical Oncology clinical practice guidelines recognize that “(neo)adjuvant trastuzumab is highly effective and should be given to all HER2-positive early breast cancer patients who do not have contraindications for its use,” with limited exceptions [2].