TRU-type lung adenocarcinomas, which are estimated to account for 75%–80% of primary lung adenocarcinomas, show histologically non-mucinous lepidic growth or papillary components and frequently express thyroid transcription factor-1 (TTF-1), which is the master regulator of lung differentiation at high levels [4–6]. This evidence concerns the gene NKX2-1 and lung adenocarcinoma.