EGFR T790M mutation caused by EGFR inhibitors (non-small-cell lung cancer), RAS mutations and MET amplification by anti-EGFR-antibody drugs (colorectal cancer), and ESR1 mutation by aromatase inhibitors (breast cancer) are representative acquired alterations, which has increasingly been elucidated. The gene discussed is EGFR; the disease is non-small cell lung carcinoma.