ABCG2 and breast cancer: Recently, our research team found that ABCG2 is associated with HER-2 expression, lymph node metastasis and clinical stage in breast invasive ductal carcinoma using immunohistochemistry (IHC) stain on the tissue microarray paraffin sections of surgically removed samples from 196 breast cancer patients with clinicopathological data, which means ABCG2 may be a novel potential prognostic bio-marker which can predict biological behavior, clinical progression, prognosis and chemotherapy effectiveness [3].