الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Bronchogenic carcinoma is malignant neoplasm of the lung arising from the epithelium of bronchus or bronchioles . Lung cancer is a disease of uncontrolled cell growth in tissue of the lung. The majority of primary lung malignancy is carcinoma. It is the most common cause of cancer related death is men and second most common cancer is women after breast cancer . In Egypt, it account for 13% of total cancer cases in both gender ranking first in male and third in female with male to female ratio 3: 1. Occupational exposure causes about 15% of lung cancer in men and 5% in women that increase the incidence in female due to increased female smokers. So, Predominance become 2: 1 . Bronchogenic carcinoma is the fifth most common tumors and represents 6% of total malignancy in registry of National Cancer Institute (NCI) in Egypt with high male predominance.According to WHO classification, the tumors of the lung is divided into squamous cell carcinoma, adenocarcinoma, large cell carcinoma. adenosquamous carcinoma, sarcomatoid carcinoma, carcinoid tumor, salivary gland tumor and preinvasive lesions . However, on clinical importance the lung cancer is broadly classified according to size of individual cells into: [1] Non Small cell lung carcinoma represents 80% which include squamous cell carcinoma, adenocarcinoma including bronchoalveolar carcinoma, large cell carcinoma. [2] Small cell lung carcinoma ”oat cell carcinoma ” represents 16% and tends to grow rapidly. Tobacco smoking is the most important aetiological factor of the lung cancer. There are other aetological factors that include radiation exposure, asbestos, and occupational inhaled substances (Nickel, chromate, arsenic and silica). Genetic mechanism including dominant oncogen (K, Ras in adenocarcinoma) and loss of tumor suppressor genes are implicated in lung cancer. It is believed to be the result of series of genetic alteration that accumulate over a period of time in pulmonary epithelial cells that leads to changes in expression of both mutated and non mutated genes . P53 Tumor suppressor gene has been shown to be inactivated either by gene mutation or loss of function of gene product . Immunohistochemistry and immunohistochemical markers have valuable role in diagnosis and differential diagnosis of different types of malignant lung epithelial tumors e.g. HMWK and CK5/6 in squamous cell carcinoma, TTF-1 in adenocarcinoma and neuroendocrine markers in neuroendocrine tumors .Also immunohistochemical markers improve sensitivity and specificity of diagnosis of bronchogenic carcinoma e.g. K1 is positive in 100% of the cases of keratinizing squamous cell carcinoma. As regard differential diagnosis, TTF-1 is extremely useful in distinguishing between primary and metastatic lung adenocarcimoa. Caludin protein has a major goal in differentiating squamous cell carcinoma from typical carcinoid . Therefore, the aim of the study is to review the literature on different histological types of malignant epithelial tumors of the lung and to evaluate the role of immunohistochemical expression in precise typing and differentiation of different pulmonary tumors.