Due to the limitations of the molecular systems, current clinical practice of breast cancer therapy is largely based upon conventional clinical and pathologic criteria, including mainly tumour stage (T), lymph node involvement (N), histological grade (G), expression of hormone receptors (HR), and hyper-expression and amplification of human epidermal growth factor receptor 2 (HER2) in the tumour tissue [2,3]. The gene discussed is ERBB2; the disease is breast cancer.