Lung cancer is cancer that begins in the lungs, the two organs found in the chest that help you breathe.

The lungs are made up of areas called lobes. The right lung has three lobes; the left lung has two, so there's room for the heart. When you breathe, air goes through your nose, down your windpipe (trachea), and into the lungs where it spreads through tubes called bronchi. Most lung cancer begins in the cells that line these tubes.

There are two main types of lung cancer:

• Non-small cell lung cancer (NSCLC) is the most common type of lung cancer.
• Small cell lung cancer makes up about 20% of all lung cancer cases.

If the lung cancer is made up of both types, it is called mixed small cell/large cell cancer.

If the cancer started somewhere else in the body and spread to the lungs, it is called metastatic cancer to the lung.

Lung cancer is the deadliest type of cancer for both men and women. Each year, more people die of lung cancer than breast, colon, and prostate cancers combined.

Lung cancer is more common in older adults. It is rare in people under age 45.

Cigarette smoking is the leading cause of lung cancer.

The more cigarettes you smoke per day and the earlier you started smoking, the greater your risk of lung cancer. There is no evidence that smoking low-tar cigarettes lowers the risk.

However, lung cancer has occurred in people who have never smoked.

Secondhand smoke (breathing the smoke of others) increases your risk of lung cancer. According to the American Cancer Society, an estimated 3,000 non-smoking adults will die each year from lung cancer related to breathing secondhand smoke.

The following may also increase one's risk of lung cancer:

• High levels of air pollution
• High levels of arsenic in drinking water
• Radon gas
• Asbestos
• Family history of lung cancer
• Radiation therapy to the lungs
• Exposure to cancer-causing chemicals such as uranium, beryllium, vinyl chloride, nickel chromates, coal products, mustard gas, chloromethyl ethers, gasoline, and diesel exhaust

Early lung cancer may not cause any symptoms. Many times, lung cancer is found when an x-ray is done for another reason.

Symptoms depend on the specific type of cancer you have, but may include:

• Cough that doesn't go away
• Coughing up blood
• Shortness of breath
• Wheezing
• Chest pain
• Loss of appetite
• Losing weight without trying
• Fatigue

Additional symptoms that may also occur with lung cancer:

• Weakness
• Swallowing difficulty
• Nail problems
• Joint pain
• Hoarseness or changing voice
• Swelling of the face
• Facial paralysis
• Eyelid drooping
• Bone pain or tenderness

These symptoms can also be due to other, less serious conditions, so it is important to talk to your health care provider.

The health care provider will perform a physical exam and ask questions about your medical history. You will be asked if you smoke, and if so, how long you have smoked.

When listening to the chest with a stethoscope, the health care provider can sometimes hear fluid around the lungs, which could (but doesn't always) suggest cancer.

Tests that may be performed include:

• Chest x-ray
• Sputum cytology test
• Blood work
• CT scan of the chest
• MRI of the chest
• Positron emission tomography (PET) scan

In some cases, the health care provider may need to remove a piece of tissue from your lungs for examination under a microscope. This is called a biopsy. There are several ways to do this:

• Bronchoscopy combined with biopsy
• Pleural biopsy
• CT scan directed needle biopsy
• Mediastinoscopy with biopsy
• Open lung biopsy

Treatment depends on the specific type of lung cancer. Each type is treated differently. Chemotherapy, radiation, and surgery may be needed.

See the individual articles on the different types of lung cancer:

• Non-small cell lung cancer
• Small cell lung cancer

How well a patient does depends on the following:

• Type of lung cancer
• Whether or not the cancer has spread
• Your age
• Your overall health
• How well you respond to treatment

The earlier the cancer is found, the better the chances of survival. Lung cancer is a deadly disease. Nearly 60% of people with lung cancer die within a year. However, some people are cured and go on to live many years.

The cancer may spread to other parts of the body (metastasis). Cancer treatment can cause significant side effects.

Call your health care provider if you develop symptoms of lung cancer (particularly if you smoke).

If you smoke, quit. It is never too late to stop smoking. You should also avoid breathing in the smoke from other people's cigarettes, cigars, or pipes.

Eating a diet rich in fruits and vegetables may help prevent some cases of lung cancer.

Mason RJ, Murray J, VC Broaddus, Nadel J. Textbook of Respiratory Medicine. 4th ed. Philadelphia, Pa: WB Saunders; 2005:1311-1409.

Gallus S. Smoking high tar cigarettes increases risk of death from lung cancer, but no differences in risk for smokers of very low, low and medium tar cigarettes. Evidence-based Healthcare. Aug 2004; 8(4); 207.

Sugimura H. Long-term survivorship in lung cancer: a review. Chest. Apr 2006; 129(4): 1088-97.