Lung cancer is the malignant transformation and expansion of lung tissue, and is the most lethal of all cancers worldwide, responsible for 1.2 million deaths annually. It is caused predominantly by cigarette smoking, and predominantly affected men, but with increased smoking among women, it is now the leading cause of death due to cancer in women.

Current research indicates that the factor with the greatest impact on risk of lung cancer is long-term exposure to inhaled carcinogens. The most common means of such exposure is tobacco smoke.

Treatment and prognosis depend upon the histological type of cancer, the stage (degree of spread), and the patient's performance status. Treatments include surgery, chemotherapy, and radiotherapy.

From http://en.wikipedia.org/wiki/Lung_cancer