EGFR and adenocarcinoma: EGFR mutations are frequently observed in adenocarcinomas as well as in Asian women who are nonsmokers.1–5 The EGFR status is the most important determining factor for tyrosine kinase inhibitor (TKI) treatment.2,4,6 EGFR mutations are found in 30% to 50% of lung adenocarcinomas, with the most common mutations being the EGFR exon 19 deletion (Ex19) and EGFR exon 21 L858R point mutation (Ex21).