Lung cancer is the most common cause of cancer death worldwide, with an estimated 1.8 million deaths each year, and adenocarcinoma is the most common histological type of lung cancer.[1]Epidermal growth factor receptor (EGFR) gene mutation is detected in 30% to 40% of lung adenocarcinoma and is associated with specific demographic parameters such as never-smoker, Asian, and female gender.[2,3] Mutations such as EGFR exon 19 deletion (19del) and L858R, which are termed “classical mutations,” comprise approximately 90% of all EGFR mutations. The gene discussed is EGFR; the disease is lung adenocarcinoma.