Lung cancer is a type of cancer that starts in the lungs. Cancer starts when cells in the body begin to grow out of control. To learn more about how cancers start and spread, see What Is Cancer?
Normal structure and function of the lungs
Your lungs are 2 sponge-like organs in your chest. Your right lung has 3 sections, called lobes. Your left lung has 2 lobes. The left lung is smaller because the heart takes up more room on that side of the body.
When you breathe in, air enters through your mouth or nose and goes into your lungs through the trachea (windpipe). The trachea divides into tubes called bronchi, which enter the lungs and divide into smaller bronchi. These divide to form smaller branches called bronchioles. At the end of the bronchioles are tiny air sacs known as alveoli.
The alveoli absorb oxygen into your blood from the inhaled air and remove carbon dioxide from the blood when you exhale. Taking in oxygen and getting rid of carbon dioxide are your lungs’ main functions.
Lung cancers typically start in the cells lining the bronchi and parts of the lung such as the bronchioles or alveoli.
A thin lining layer called the pleura surrounds the lungs. The pleura protects your lungs and helps them slide back and forth against the chest wall as they expand and contract during breathing.
Below the lungs, a thin, dome-shaped muscle called the diaphragm separates the chest from the abdomen. When you breathe, the diaphragm moves up and down, forcing air in and out of the lungs.
What are the symptoms of lung cancer?
Sometimes lung cancer does not cause any signs or symptoms. It may be found during a chest x-ray done for another condition.
- Chest pain or discomfort
- A cough that doesn’t go away or gets worse over time
- Trouble breathing
- Wheezing
- Blood in sputum (mucus coughed up from the lungs)
- Hoarseness
- Loss of appetite
- Weight loss for no known reason
- Fatigue
- Trouble swallowing
- Swelling in the face and/or veins in the neck
How is lung cancer diagnosed?
Your health care provider may use many tools to make a diagnosis:
- A medical history, which includes asking about your symptoms
- A family history
- A physical exam
- Imaging tests, such as a chest x-ray or chest CT scan
- Lab tests, including tests of your blood and sputum
- A biopsy of the lung
Causes of lung cancer
Factors that can increase your risk of lung cancer include:
- smoking tobacco
- second-hand (passive) smoking
- exposure to asbestos
- exposure to radon (radioactive gas)
- exposure to occupational substances such as arsenic, cadmium, nickel, diesel fumes and soot
- HIV infection
- family history
