In non-small cell lung cancers (NSCLCs), the discovery of activating mutations in the epidermal growth factor receptor (EGFR) gene such as the missense mutation L858R within exon 21 and short in-frame deletions within exon 19 have ushered in a new era of genomics-guided precision targeted therapy in lung cancer. The gene discussed is EGFR; the disease is lung carcinoma.