The identification of activating mutations in the gene encoding the epidermal growth factor receptor (EGFR) tyrosine kinase in patients with non-small cell lung cancer (NSCLC) and the subsequent development of targeted therapy with small-molecule EGFR tyrosine kinase inhibitors (TKIs) has dramatically revolutionised the treatment landscape of these tumours. The gene discussed is EGFR; the disease is neoplasm.