<h4>Background</h4>Activating mutations in the epidermal growth factor receptor (EGFR), particularly exon 19 deletions and L858R mutation, are frequently observed in non-small cell lung cancer (NSCLC) and confer sensitivity to EGFR-tyrosine kinase inhibitors (EGFR-TKIs). The gene discussed is EGFR; the disease is non-small cell lung carcinoma.