Trastuzumab (herceptin) is a humanized, recombinant monoclonal antibody that binds to the extracellular, juxtamembrane domain of HER2, and is standard care for patients whose breast cancer cells show strong immunohistochemical staining for HER2 or moderate immunohistochemical staining with HER2/neu gene amplification [2]. Here, ERBB2 is linked to breast carcinoma.