Distinct subsets of adenocarcinoma with morphologic differentiation to type II pneumocytes, Clara cells, or non-ciliated bronchioles are thought to originate from the terminal respiratory unit (TRU), and EGFR mutation is involved with early-stage carcinogenesis of TRU-type adenocarcinoma[5,37]; nGGOs appear to be another marker of TRU-type adenocarcinoma[5]. The gene discussed is EGFR; the disease is adenocarcinoma.