Lung cancer is a kind of cancer that starts as a growth of cells in the lungs. The lungs are two spongy organs in the chest that control breathing.

Lung cancer is the leading cause of cancer deaths worldwide.

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 smoked. Quitting smoking, even after smoking for many years, significantly lowers the chances of developing lung cancer. Lung cancer also can happen in people who have never smoked.


Lung cancer typically doesn't cause symptoms early on. Symptoms of lung cancer usually happen when the disease is advanced.

Signs and symptoms of lung cancer that happen in and around the lungs may include:

  • A new cough that doesn't go away.
  • Chest pain.
  • Coughing up blood, even a small amount.
  • Hoarseness.
  • Shortness of breath.
  • Wheezing.

Signs and symptoms that happen when lung cancer spreads to other parts of the body may include:

  • Bone pain.
  • Headache.
  • Losing weight without trying.
  • Loss of appetite.
  • Swelling in the face or neck.

When to see a doctor

Make an appointment with your doctor or other healthcare professional if you have any symptoms that worry you.

If you smoke and haven't been able to quit, make an appointment. Your healthcare professional can recommend strategies for quitting smoking. These may include counseling, medicines and nicotine replacement products.

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Lung cancer happens when cells in the lungs develop changes in their DNA. A cell's DNA holds the instructions that tell a cell what to do. In healthy cells, the DNA gives instructions to grow and multiply at a set rate. The instructions tell the cells to die at a set time. In cancer cells, the DNA changes give different instructions. The changes tell the cancer cells to make many more cells quickly. Cancer cells can keep living when healthy cells would die. This causes too many cells.

The cancer cells might form a mass called a tumor. The tumor can grow to invade and destroy healthy body tissue. In time, cancer cells can break away and spread to other parts of the body. When cancer spreads, it's called metastatic cancer.

Smoking causes most lung cancers. It can cause lung cancer in both people who smoke and in people exposed to secondhand smoke. But lung cancer also happens in people who never smoked or been exposed to secondhand smoke. In these people, there may be no clear cause of lung cancer.

How smoking causes lung cancer

Researchers believe smoking causes lung cancer by damaging the cells that line the lungs. Cigarette smoke is full of cancer-causing substances, called carcinogens. When you inhale cigarette smoke, the carcinogens cause changes in the lung tissue almost immediately.

At first your body may be able to repair this damage. But with each repeated exposure, healthy cells that line your lungs become more damaged. Over time, the damage causes cells to change and eventually cancer may develop.

Types of lung cancer

Lung cancer is divided into two major types based on the appearance of the cells under a microscope. Your healthcare professional 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 usually only happens in people who have smoked heavily for years. Small cell lung cancer is less common than non-small cell lung cancer.
  • Non-small cell lung cancer. Non-small cell lung cancer is a category that includes several types of lung cancers. Non-small cell lung cancers include squamous cell carcinoma, adenocarcinoma and large cell carcinoma.

Risk factors

A number of factors may increase the risk of lung cancer. Some risk factors can be controlled, for instance, by quitting smoking. Other factors can't be controlled, such as your family history.

Risk factors for lung cancer include:


Your risk of lung cancer increases with the number of cigarettes you smoke each day. Your risk also increases with the number of years you have smoked. Quitting at any age can significantly lower your risk of developing lung cancer.

Exposure to secondhand smoke

Even if you don't smoke, your risk of lung cancer increases if you're around people who are smoking. Breathing the smoke in the air from other people who are smoking is called secondhand smoke.

Previous radiation therapy

If you've had radiation therapy to the chest for another type of cancer, you may have an increased risk of developing lung cancer.

Exposure to radon gas

Radon is produced by the natural breakdown of uranium in soil, rock and water. Radon eventually becomes part of the air you breathe. Unsafe levels of radon can build up in any building, including homes.

Exposure to cancer-causing substances

Workplace exposure to cancer-causing substances, called carcinogens, can increase your risk of developing lung cancer. The risk may be higher if you smoke. Carcinogens linked to lung cancer risk include asbestos, arsenic, chromium and nickel.

Family history of lung cancer

People with a parent, sibling or child with lung cancer have an increased risk of the disease.


Lung cancer can cause complications, such as:

Shortness of breath

People with lung cancer can experience shortness of breath if cancer grows to block the major airways. Lung cancer also can cause fluid to collect around the lungs and heart. The fluid makes it harder for the affected lung to expand fully when you inhale.

Coughing up blood

Lung cancer can cause bleeding in the airway. This can cause you to cough up blood. Sometimes bleeding can become severe. Treatments are available to control bleeding.


Advanced lung cancer that spreads can cause pain. It may spread to the lining of a lung or to another area of the body, such as a bone. Tell your healthcare professional if you experience pain. Many treatments are available to control pain.

Fluid in the chest

Lung cancer can cause fluid to accumulate in the chest, called pleural effusion. The fluid collects in the space that surrounds the affected lung in the chest cavity, called the pleural space.

Pleural effusion can cause shortness of breath. Treatments are available to drain the fluid from your chest. Treatments can reduce the risk that pleural effusion will happen again.

Cancer that spreads to other parts of the body

Lung cancer often spreads to other parts of the body. Lung cancer may spread to the brain and the bones.

Cancer that spreads can cause pain, nausea, headaches or other symptoms depending on what organ is affected. Once lung cancer has spread beyond the lungs, it's generally not curable. Treatments are available to decrease symptoms and to help you live longer.


There's no sure way to prevent lung cancer, but you can reduce your risk if you:

Don't smoke

If you've never smoked, don't start. Talk to your children about not smoking so that they can understand how to avoid this major risk factor for lung cancer. Begin conversations about the dangers of smoking with your children early so that they know how to react to peer pressure.

Stop smoking

Stop smoking now. Quitting reduces your risk of lung cancer, even if you've smoked for years. Talk to your healthcare team about strategies and aids that can help you quit. Options include nicotine replacement products, medicines and support groups.

Avoid secondhand smoke

If you live or work with a person who smokes, urge them to quit. At the very least, ask them to smoke outside. Avoid areas where people smoke, such as bars. Seek out smoke-free options.

Test your home for radon

Have the radon levels in your home checked, especially if you live in an area where radon is known to be a problem. High radon levels can be fixed to make your home safer. Radon test kits are often sold at hardware stores and can be purchased online. For more information on radon testing, contact your local department of public health.

Avoid carcinogens at work

Take precautions to protect yourself from exposure to toxic chemicals at work. Follow your employer's precautions. For instance, if you're given a face mask for protection, always wear it. Ask your healthcare professional what more you can do to protect yourself at work. Your risk of lung damage from workplace carcinogens increases if you smoke.

Eat a diet full of fruits and vegetables

Choose a healthy diet with a variety of fruits and vegetables. Food sources of vitamins and nutrients are best. Avoid taking large doses of vitamins in pill form, as they may be harmful. For instance, researchers hoping to reduce the risk of lung cancer in people who smoked heavily gave them beta carotene supplements. Results showed the supplements increased the risk of cancer in people who smoke.

Exercise most days of the week

If you don't exercise regularly, start out slowly. Try to exercise most days of the week.

April 30, 2024

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