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Lung cancer is a type of cancer that begins in the lungs. Your lungs are two spongy organs in your chest that take in oxygen when you inhale and release carbon dioxide when you exhale. Lung cancer is the leading cause of cancer deaths worldwide. People who smoke have the greatest risk of lung cancer, though lung cancer can also occur in people who have never smoked. The risk of lung cancer increases with the length of time and number of cigarettes you’ve smoked. If you quit smoking, even after smoking for many years, you can significantly reduce your chances of developing lung cancer. Symptoms Lung cancer typically doesn’t cause signs and symptoms in its earliest stages. Signs and symptoms of lung cancer typically occur when the disease is advanced. A new cough that doesn’t go away Coughing up blood, even a small amount Shortness of breath Chest pain Hoarseness Losing weight without trying Bone pain Headache Causes Smoking causes the majority of lung cancers both in smokers and in people exposed to secondhand smoke. But lung cancer also occurs in people who never smoked and in those who never had prolonged exposure to secondhand smoke. In these cases, there may be no clear cause of lung cancer.