It has been suggested that NSCLC subtypes can be distinguished using several immunohistochemical markers, such as napsin A and thyroid transcription factor 1 (TTF-1) in adenocarcinoma and tumor protein 63 (p63) and protein 40 (p40), which are frequently expressed in squamous cell carcinoma [5]. The gene discussed is TTF1; the disease is adenocarcinoma.