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 in the United States, among both men and women. Lung cancer claims more lives each year than do colon, prostate, ovarian and breast cancers combined.
People who smoke have the greatest risk of lung cancer. 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.
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.
How smoking causes lung cancer
Doctors believe smoking causes lung cancer by damaging the cells that line the lungs. When you inhale cigarette smoke, which is full of cancer-causing substances (carcinogens), changes in the lung tissue begin almost immediately.
At first your body may be able to repair this damage. But with each repeated exposure, normal cells that line your lungs are increasingly damaged. Over time, the damage causes cells to act abnormally and eventually cancer may develop.
Doctors divide lung cancer into two major types based on the appearance of lung cancer cells under the microscope. Your doctor makes treatment decisions based on which major type of lung cancer you have. The two general types of lung cancer include:
- Small cell lung cancer. Small cell lung cancer occurs almost exclusively in heavy smokers and is less common than non-small cell lung cancer.
- Non-small cell lung cancer. Non-small cell lung cancer is an umbrella term for several types of lung cancers that behave in a similar way. Non-small cell lung cancers include squamous cell carcinoma, adenocarcinoma and large cell carcinoma.
Lung cancer typically doesn’t cause signs and symptoms in its earliest stages. Signs and symptoms of lung cancer typically occur only when the disease is advanced.
Signs and symptoms of lung cancer may include:
- A new cough that doesn’t go away
- Changes in a chronic cough or “smoker’s cough”
- Coughing up blood, even a small amount
- Shortness of breath
- Chest pain
- Losing weight without trying
- Bone pain
Make an appointment with your doctor if you have any signs or symptoms that worry you.
If you smoke and have been unable to quit, make an appointment with your doctor. Your doctor can recommend strategies for quitting smoking, such as counseling, medications and nicotine replacement products.