The 2011 International Association for the Study of Lung Cancer (IASLC)/American Thoracic Society/European Respiratory Society guidelines strongly encourage surgical pathologists to minimize the amount of tissue used for diagnosis, in particular by limiting the number of first-line IHC stains.6Thus, this study aimed at evaluating the most useful limited IHC panel including TTF1, Napsin A, p63, and p40 for subclassifying NSCLC. This evidence concerns the gene TTF1 and non-small cell lung carcinoma.