Lung cancer is a disease of uncontrolled cell growth in tissues (tissue (biology)) of the lung. This growth may lead to metastasis, which is the invasion of adjacent tissue and infiltration beyond the lungs. The vast majority of primary lung cancers are carcinomas of the lung, derived from epithelial (epithelium) cells. Lung cancer, the most common cause of cancer-related death in men and also the most common in women, is responsible for 1.3 million deaths (:Category:Deaths from lung cancer) worldwide annually. The most common symptoms are shortness of breath, coughing (including coughing up blood (Hemoptysis)), and weight loss.

The main types of lung cancer are small cell lung carcinoma and non-small cell lung carcinoma. This distinction is important, because the treatment varies; non-small cell lung carcinoma (NSCLC) is sometimes treated with surgery (lung cancer surgery), while small cell lung carcinoma (SCLC) usually responds better to chemotherapy and radiation. The most common cause of lung cancer is long-term exposure to tobacco smoke (tobacco smoking). The occurrence of lung cancer in nonsmokers, who account for as many as 15% of cases , is often attributed to a combination of genetic factors (genetics), radon gas, asbestos, and air pollution, including secondhand smoke (passive smoking).

Lung cancer may be seen on chest radiograph and computed tomography (CT scan). The diagnosis (medical diagnosis) is confirmed with a biopsy. This is usually performed via bronchoscopy or CT-guided biopsy. Treatment and prognosis depend upon the histological (histology) type of cancer, the stage (staging (pathology)) (degree of spread), and the patients performance status. Possible treatments include surgery, chemotherapy, and radiotherapy (radiation therapy). With treatment, the five-year survival rate is 14%.