Immunostaining of cytology specimens. A) TTF1 positive adenocarcinoma in cell block specimen (by brown 3,3’-diamonobenzidine, Ventana Benchmark XT immunostainer), BE) immunostaining on Papanicolaou stained, ethanol fixed, non-cell block specimens (Leica Bond automated immunostainer); B) TTF1 positive adenocarcinoma (detection by red 3-amino-9 ethylcarbazole), C) p40 positive non-keratinizing squamous cell carcinoma, D) p40 positive benign hyperplastic basal cells underlying ciliated respiratory cells (bronchial brush cytology), E: CD56 positive small cell carcinoma with corresponding Papanicolaou stained specimen (F).