With the evidence available today, it is left to clinical judgment to determine whether patients with equivocal HER2-positivity based on ASCO/CAP or with a tumor size of 0.6 to 1.0 cm should be given trastuzumab, and what level of cardiac risk warrants less cardiotoxic trastuzumab regimens, namely, those with a shorter duration of trastuzumab, sequential use, and the avoidance of anthracyclines. The gene discussed is ERBB2; the disease is neoplasm.