ERBB2 and breast cancer: A new electrochemical immunosensor is developed to simultaneously detect 3 early breast cancer biomarker antigens mucin1 (MUC1), cancer antigen 15–3 (CA15-3), and human epidermal growth factor receptor 2 (HER2) with a detection limit of < 2 ng/ml which is significantly lower than the clinically relevant cut-off values [205].