Using tissue microarrays from 657 surgically treated primary lung cancers, we evaluated the mucin stains periodic acid-Schiff with diastase (PASD), alcian blue–periodic acid-Schiff (ABPAS) and mucicarmine, and compared with the IHC markers p40, p63, cytokeratin 5, thyroid transcription factor 1 (TTF-1), napsin A and cytokeratin 7. The gene discussed is TTF1; the disease is lung cancer.