The HER2/neu protein is over-expressed in 20-30% of invasive human breast cancers [15,16], is associated with aggressive disease [15,17] and has been successfully targeted in HER2/neu+, hormone receptor positive or negative, breast cancer patients with trastuzumab (Herceptin®) [18-20], which is a humanized monoclonal antibody directed against the extracellular domain of the HER2/neu protein. This evidence concerns the gene ERBB2 and breast cancer.