EGFR mutations are detected in 20% to 50% of lung adenocarcinoma patients, EGFR exon 20 insertions are the next most common EGFR mutations in NSCLC after classical mutations, accounting for 4% to 10% of all observed EGFR aberration.[5,6] Most EGFR exon 20 insertion mutations predict resistance to clinically achievable levels of tyrosine kinase inhibitors (TKIs) in advanced NSCLC, although there are rare exceptions. The gene discussed is EGFR; the disease is lung adenocarcinoma.