ERBB2 and cancer: In particular, trastuzumab—the monoclonal antibody directed against the extracellular domain of the human epidermal growth factor receptor 2 (HER2)—is still the only treatment that is effective against the altered product of an oncogene, the erythroblastic leukemia viral oncogene homolog 2 (ERB-B2), which is amplified in a range from 12 to 23% in EG cancer patients.