الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Lung cancer is a leading cause of cancer related mortality in many countries being responsible for 1.1 million deaths annually. Many risk factors can be responsible for lung cancer such as smoking, radon, asbestos, COPD& positive family history. Many genetic alteration have also been implicated in lung cancer especially in never smokers. Due to rapid advances in clinical, radiologic, pathologic & molecular aspects of lung cancer there’s a need to improve existing WHO 2004 classification using a multidisciplinary approach. This previous classification replaced now by proposed IASCLC/ATS/ARS classification of lung cancer in small biopsies as 70% of lung cancer are diagnosed in small biopsies. One of the major changes in the classification is that the term bronchioloalveolar carcinoma is no longer used and replaced by term lepidic predominant adenocarcinoma. Also IASCLC recommended importance of distinguishing SQCC, ADC, NSCLC (NOS) and neuroendocrine tumor and assist in determining patient therapy. Immunohistochemical markers have variable role in diagnosis and differential diagnosis of different types of malignant epithelial tumors of the lung. We aim to minimize term NSCLC (NOS) as little as possible and a minimal panel can be used for differential diagnosis of different histologic subtypes. We used Napsin A for adenocarcinoma – CK5/6 for squamous cell carcinoma cases – CD56 for neuroendocrine tumors .Napsin A is superior to TTF-1 in distinguishing primary lung adenocarcinoma from other carcinoma (except kidney). Also, use of polyclonal Napsin A reduce the specificity. Finally, immunohistochemistry represent the most reliable and affordable method among different method of diagnosis and it has a major goal in differentiating different types of pulmonary tumors.