In our previous study [3], we found the expression of ABCG2 protein correlated with Her-2 expression, lymph node metastasis and clinical stage in breast invasive ductal carcinoma and ABCG2 could be a novel potential bio-marker which can predict biological behavior, clinical progression, prognosis and chemotherapy effectiveness. The gene discussed is ABCG2; the disease is invasive ductal breast carcinoma.