Two common EGFR somatic alterations, the L858R mutation in exon 21 and exon 19 in-frame deletions encompassing amino acids 747 to 749, represent about 90% of EGFR mutations in lung adenocarcinoma, and predict clinical responses to EGFR-TKIs [7–12]. The gene discussed is EGFR; the disease is lung adenocarcinoma.