Lung Carcinoma: Abrief discussion of various types of lung carcinoma.

Lung carcinomaLung cancer is one of the commonly occurring cancers and currently is the leading contributor to the deaths related to cancers worldwide. The global rise in lung cancer incidence, together with the fact that the overall 5-year survival of patients with this disease is less than 15%, underscores the magnitude of the lung cancer epidemic. The current chapter focuses on recent developments regarding the diagnosis, treatment, and prevention of non small cell lung cancer (NSCLC). The vast majority of NSCLCs are caused by cigarette smoking. Cigarette smoke contains over 300 chemicals, 40 of which are known to be potent carcinogens. Of particular significance, nitrosamine 4-(methylnitrosamino)-1-(3-pyridil)-1-butanone (NNK), and polycyclic aromatic hydrocarbons (PAHs) such as benzo[a]pyrene induce pulmonary carcinomas in rodents that exhibit histologic and molecular genetics profiles virtually identical to those of human lung cancers. Whereas the vast majority of lung cancers are attributable to cigarette smoking, fewer than 20% of smokers develop this disease. Although these observations suggest a genetic predisposition to lung cancer, to date, the genes conferring susceptibility to this disease remain elusive.The designation non small cell carcinoma of the lung refers to a group of commonly observed pulmonary neoplasm’s that are typically associated with cigarette smoking and share the common property of not being responsive to small cell carcinoma treatment protocols. Through the 1960s, the predominant type of non small cell carcinoma was squamous cell carcinoma. Although the overall incidence of lung cancer has dramatically increased over the past 30 years, the relative incidence of squamous cell carcinoma has decreased, and adenocarcinoma has become the dominant cell type. Large cell carcinomas are composed of large cells without cytoplasmic differentiation and account for approximately 15% of all lung cancers. Squamous cell carcinoma may present clinically in the periphery of the lung as a small sub pleural nodule with the gross appearance and overall prognosis of a peripheral adenocarcinoma. However, squamous cell carcinoma typically arises in proximal segmental bronchi via progression through stages of dysplasia. In its earliest form (carcinoma in situ), malignant squamous cells spread over the bronchial surface, often involving sub mucosal glands, without invasion through the basement membrane.The signs and symptoms manifested by patients suffering from lung cancer depend on the histologic features of the tumor and the extent of loco regional invasion, as well as the location, size, and number of distant metastases. Many patients present with an asymptomatic lesion discovered incidentally on chest radiograph. Tumors arising in the larger airways may cause persistent cough, wheezing, or haemoptysis. Typically, patients with haemoptysis experience blood-streaked sputum; massive bleeding is rarely seen at presentation. Continued growth of endobronchial tumors frequently results in atelectasis with or without pneumonia and abscess. If pleural surfaces are involved, either by the primary tumor or associated infection, pleuritic pain may develop with or without detectable pleural effusion. The loss of lung function usually is associated with dyspnoea, the severity of which depends on the amount of lung involved and the patient’s underlying pulmonary reserve. Depending on its location, the primary tumor can invade the chest wall, producing either stabbing or burning radicular pain or pleural effusion.