Doctors cannot always explain why one person develops lung cancer and another does not. However, we do know that a person with certain risk factors may be more likely than others to develop lung cancer. A risk factor is something that may increase the chance of developing a disease.

Risk Factors for Lung Cancer

Tobacco smoke: Tobacco smoke causes most cases of lung cancer. It's by far the most important risk factor for lung cancer. Harmful substances in smoke damage lung cells. That's why smoking cigarettes, pipes, or cigars can cause lung cancer and why secondhand smoke can cause lung cancer in nonsmokers. The more a person is exposed to smoke, the greater the risk of lung cancer.

Radon: Radon is a radioactive gas that you cannot see, smell, or taste. It forms in soil and rocks. People who work in mines may be exposed to radon. In some parts of the country, radon is found in houses. Radon damages lung cells, and people exposed to radon are at increased risk of lung cancer. The risk of lung cancer from radon is even higher for smokers.

Asbestos and other substances: People who have certain jobs (such as those who work in the construction and chemical industries) have an increased risk of lung cancer. Exposure to asbestos, arsenic, chromium, nickel, soot, tar, and other substances can cause lung cancer. The risk is highest for those with years of exposure. The risk of lung cancer from these substances is even higher for smokers.

Air pollution: Air pollution may slightly increase the risk of lung cancer. The risk from air pollution is higher for smokers.

Family history of lung cancer: People with a father, mother, brother, or sister who had lung cancer may be at slightly increased risk of the disease, even if they don't smoke.

Personal history of lung cancer: People who have had lung cancer are at increased risk of developing a second lung tumor.

Over 65 years old: Most people are older than 65 years when diagnosed with lung cancer.

Browse Our Free Senior Care Guides

Researchers have studied other possible risk factors. For example, having certain lung diseases (such as tuberculosis or bronchitis) for many years may increase the risk of lung cancer. It's not yet clear whether having certain lung diseases is a risk factor for lung cancer.

People who think they may be at risk for developing lung cancer should talk to their doctor. The doctor may be able to suggest ways to reduce their risk and can plan an appropriate schedule for checkups. For people who have been treated for lung cancer, it's important to have checkups after treatment. The lung tumor may come back after treatment, or another lung tumor may develop.

Symptoms of Lung Cancer

Early lung cancer often does not cause symptoms. But as the cancer grows, common symptoms may include:

  • A cough that gets worse or does not go away breathing trouble, such as shortness of breath
  • Constant chest pain
  • Coughing up blood
  • A hoarse voice
  • Frequent lung infections, such as pneumonia
  • Feeling very tired all the time
  • Weight loss with no known cause

Most often these symptoms are not due to cancer. Other health problems can cause some of these symptoms. Anyone with such symptoms should see a doctor to be diagnosed and treated as early as possible.

Testing for Lung Cancer

If you have a symptom that suggests lung cancer, your doctor must find out whether it's from cancer or something else. Your doctor may ask about your personal and family medical history. Your doctor may order blood tests, and you may have one or more of the following tests:

  • Physical exam: Your doctor checks for general signs of health, listens to your breathing, and checks for fluid in the lungs. Your doctor may feel for swollen lymph nodes and a swollen liver.
  • Chest x-ray: X-ray pictures of your chest may show tumors or abnormal fluid.
  • CT scan: Doctors often use CT scans to take pictures of tissue inside the chest. An x-ray machine linked to a computer takes several pictures. For a spiral CT scan, the CT scanner rotates around you as you lie on a table. The table passes through the center of the scanner. The pictures may show a tumor, abnormal fluid, or swollen lymph nodes.

Collecting Cells or Tissue Samples

The only sure way to know if lung cancer is present is for a pathologist to check samples of cells or tissue. The pathologist studies the sample under a microscope and performs other tests. There are many ways to collect samples. Your doctor may order one or more of the following tests to collect samples:

  • Sputum cytology: Thick fluid (sputum) is coughed up from the lungs. The lab checks samples of sputum for cancer cells.
  • Thoracentesis: The doctor uses a long needle to remove fluid (pleural fluid) from the chest. The lab checks the fluid for cancer cells.
  • Bronchoscopy: The doctor inserts a thin, lighted tube (a bronchoscope) through the nose or mouth into the lung. This allows an exam of the lungs and the air passages that lead to them. The doctor may take a sample of cells with a needle, brush, or other tool. The doctor also may wash the area with water to collect cells in the water.
  • Fine-needle aspiration: The doctor uses a thin needle to remove tissue or fluid from the lung or lymph node. Sometimes the doctor uses a CT scan or other imaging method to guide the needle to a lung tumor or lymph node.
  • Thoracoscopy: The surgeon makes several small incisions in your chest and back. The surgeon looks at the lungs and nearby tissues with a thin, lighted tube. If an abnormal area is seen, a biopsy to check for cancer cells may be needed.
  • Thoracotomy: The surgeon opens the chest with a long incision. Lymph nodes and other tissue may be removed.
  • Mediastinoscopy: The surgeon makes an incision at the top of the breastbone. A thin, lighted tube is used to see inside the chest. The surgeon may take tissue and lymph node samples.

Questions to Ask Before the Doctor Takes a Sample

  1. Which procedure do you recommend?
  2. How will the tissue be removed?
  3. Is a hospital stay required? If so, for how long?
  4. Are there preparations to take before the test?
  5. How long will it take?
  6. Are you awake?
  7. Will it hurt?
  8. What are there any risks?
  9. What is the chance that the procedure will cause the lungs to collapse?
  10. What are the chances of infection or bleeding after the procedure?
  11. How long will it take to recover?
  12. How soon will we have the results? Who will explain the results?
  13. If cancer is found, who will talk about the next steps? When?

Types of Lung Cancer

The pathologist checks the sputum, pleural fluid, tissue, or other samples for cancer cells. If cancer is found, the pathologist reports the type. The types of lung cancer are treated differently. The most common types are named for how the lung cancer cells look under a microscope:

  • Small cell lung cancer: About 13 percent of lung cancers are small cell lung cancers. This type tends to spread quickly.
  • Non-small cell lung cancer: Most lung cancers (about 87 percent) are non-small cell lung cancers. This type spreads more slowly than small cell lung cancer.

The National Cancer Institute (NCI) is part of the National Institutes of Health (NIH), which is one of 11 agencies that comprise the U.S. Public Health Service (PHS) in the Department of Health and Human Services (HHS).