<p><p> Primary tumours of the lung consist of four principal types; squamous cell carcinoma, small cell carcinoma, large cell </p> <div>carcinoma and adenocarcinoma. The results of several clinical trials identified lung tumor histologic features as a </div> <div>potential prognostic factor and predictor of clinical outcome and response to chemotherapy. Hence, the distinction </div> <div>between different subtypes of NSCLC, particularly adenocarcinoma and squamous cell carcinoma (SCC) has gained importance. Cytologic </div> <div>features of these tumors can overlap, and a variety of superimposed degenerative and mechanical changes can distort the cytologic appearances </div> <div>of the tumor cells. As a result, ancillary techniques such as immunohistochemical analysis have been frequently incorporated into the diagnostic </div> <div>workup of many cytologic and small biopsy specimens.CK5/6 and p63 were used as immunohistochemical markers for SCC, and TTF–1 and </div> <div>surfactant protein A were markers for Adenocarcinoma</div></p>