Thyroid transcription factor‐1 (TTF‐1, encoded by the NKX2‐1 gene) is highly expressed in small‐cell lung carcinoma (SCLC) and lung adenocarcinoma (LADC), but how its functional roles differ between SCLC and LADC remains to be elucidated. The gene discussed is NKX2-1; the disease is lung adenocarcinoma.