In retrospective analysis of breast cancer trials, HER2E tumors with HER2 amplification were observed to benefit most from anti-HER2 agents, luminal A and B tumors with HER2 amplification were likely to benefit from anti-HER2 targeted therapy, and basal-like tumors with HER2 amplification benefited least [8–11]. The gene discussed is ERBB2; the disease is breast cancer.