ERBB2 and breast cancer: HER2 positivity (HER2+), a subtype of breast cancer characterized by either HER2 protein overexpression or gene amplification, is found in approximately 15%–30% of breast cancers and contributes with low survival and poor clinical outcome in breast cancer patient.13 This reduced survival is closely related to aggressive proliferation of HER2-overexpressing cells14; as well as the occurrence of breast cancer metastasis as HER2 overexpression increases the invasive potential of cancer cells.