Lung Cancer Basics

Key Points

  • Lung cancer happens when cells in the lung change (mutate). They grow uncontrollably and cluster together to form a tumor.
  • Lung cells most often change because they are exposed to dangerous chemicals that we breathe.
  • There are two main types of lung cancer, small cell lung cancer and non-small cell lung cancer. Non-small cell lung cancer is more common.
  • Lung cancer symptoms usually do not appear until the cancer has spread to other parts of the body. At this point, it is harder to treat lung cancer.

What is Lung Cancer?

Lung cancer is a cancer that starts in the lungs. When a person has lung cancer, they have abnormal cells that cluster together to form a tumor. Unlike normal cells, cancer cells grow without order or control and destroy the healthy lung tissue around them. These types of tumors are called malignant tumors. When the cancer cells grow too fast, they prevent organs of the body from functioning properly.

What are the types of lung cancer?

Non-Small Cell Small Cell Carcinoma Adenocarcinoma Squamous Cell Carcinoma Large Cell Carcinoma

  • Non-small cell lung cancer is the more common form of lung cancer.
  • Small cell lung cancer is almost always associated with cigarette smoking.
  • Each sub type of non-small cell lung cancer is different, but they are grouped together because they are treated similarly.
  • The types of small cell lung cancer are named for the kinds of cells found in the cancer and how the cells look when viewed under a microscope.

Just as each person is unique, each type of lung cancer is different. It is important to know the type of lung cancer you have, sometimes called “your lung cancer profile” because it helps determine what lung cancer treatment options are available. When you know your lung cancer profile, you and your care team can set lung cancer treatment goals.

What Causes Lung Cancer?

Anyone can get lung cancer. Lung cancer occurs when cells in the lung mutate or change. Various factors can cause this mutation to happen. Most often, this change in lung cells happens when people breathe in dangerous, toxic substances. Even if you were exposed to these substances many years ago, you are still at risk for lung cancer. Talk to your doctor if you have ever been exposed to any of the substances listed below.


Smoking is the number one cause of lung cancer. It causes about 87 percent of lung cancer cases. Tobacco smoke contains many chemicals that are known to cause lung cancer. Smokers are not the only ones affected by cigarette smoke. Nonsmokers can breathe in secondhand smoke and develop lung cancer or other illnesses.
Learn How to Quit Smoking »


Radon exposure is the second leading cause of lung cancer. Radon is a colorless, odorless radioactive gas that exists naturally in soil. It comes up through the soil and enters buildings through small gaps and cracks. One out of every 15 homes in the U.S. is subject to radon exposure. Exposure to radon combined with cigarette smoking seriously increases your lung cancer risk. More »

Hazardous Chemicals

Exposure to certain hazardous chemicals poses a lung cancer risk. Working with materials such as asbestos, uranium, arsenic, cadmium, chromium, nickel and some petroleum products is especially dangerous. If you think you may be breathing in hazardous chemicals at your job, talk to your employer and your doctor to find out how you can protect yourself. More »

Particle Pollution

Particle pollution refers to a mix of very tiny solid and liquid particles that are in the air we breathe. Evidence shows that particle pollution—like that coming from that exhaust smoke—can increase the risk of lung cancer. More »


Genetic factors also play a role in one’s chances of developing lung cancer. Mutations in several genes have been linked to lung cancer. This suggests that there is a genetic component to lung cancer. A family history of lung cancer may mean you are at a higher risk of getting the disease.

Lung cancer—the number one cancer killer in America—stands on the precipice of change.

One reason lung cancer is so deadly is that it is hard to find in its early stages. It may take years for the lung cancer to grow. Early on there are usually no symptoms of lung cancer. By the time a patient starts to notice symptoms of lung cancer, the cancer has often spread to other parts of the body.

How is lung cancer diagnosed?

Researchers are working hard to develop lung cancer screening tests that can detect lung cancer in its early stages. Lung cancer treatment is more successful when it is found early. A recent study found that lung cancer screening with low dose CT scans can reduce deaths in those with a high lung cancer risk. Talk to your doctor to determine if you are a candidate for lung cancer screening if you have not been diagnosed yet.

Researchers are also studying new lung cancer treatments to help people live longer and find a cure for lung cancer. Your doctor can answer questions about whether or not a new and emerging lung cancer treatment might be right for you. 

However, not all lung cancer is caused by smoking and these other known risks. For some, the reason is never identified. Continued work to prevent lung cancer and research to improve lung cancer diagnosis and treatment is critical.