Lung cancer is the most common type of cancer in both men and women in this country. According to the American Cancer Society, almost 220,000 people are diagnosed with it each year. Most cases are linked to tobacco smoking.
The lungs, which help you breathe, are two sponge-like, cone-shaped organs in the chest. When you breathe in, oxygen comes through your mouth and nose. It then travels through the windpipe (trachea), which divides into two tubes called bronchi. These take the oxygen to the left and right lungs. The inside of the lungs includes smaller branches called bronchioles and alveoli, which are tiny air sacs.
Each lung is divided into sections called lobes. The right lung has three lobes. The left lung, which has two lobes, is smaller than the right lung because the heart is also on the left side of the body.
The pleura is a thin membrane that covers the outside of each lung and lines the inside wall of the chest. It usually contains a small amount of fluid and forms a protective lining around the lungs that allows them to move smoothly during breathing.
Cancer Grows in Lungs, May Spread
Lung cancer forms in the tissues of the lungs, most often in the cells that line air passages. It occurs when cells in your lungs grow and multiply uncontrollably, damaging surrounding tissue and interfering with the lungs’ normal function.
Lung cancer may spread through your lymph system. Lymph is a clear fluid that contains tissue waste and cells that help fight infection. It travels through your body in vessels that are similar to veins. Lymph nodes are small, bean-shaped organs that link lymph vessels.
Cancer cells can spread, or metastasize, to other parts of your body through the bloodstream as well. When lung cancer spreads to other organs, it still is called lung cancer.
Lung Cancer Types
Lung cancer is classified by the type of cells within the tumor. Each type of lung cancer grows and is treated in a different way. Lung cancers are divided into two main groups.
Non-small cell lung cancer (NSCLC): This is the most common type of lung cancer. The categories of non-small cell lung cancer are named for the type of cells in the cancer:
Adenocarcinoma begins in cells that line the alveoli and make mucus. It is found more often in nonsmokers, women and younger people.
Squamous cell carcinoma (cancer) begins in thin, flat cells in the lungs, and tobacco smoking most often causes it. It also is called epidermoid carcinoma.
Large cell carcinoma (cancer) begins in certain types of large cells in the lungs.
Small cell lung cancer: Also known as oat-cell cancer, this type of lung cancer makes up less than 20% of lung cancers and almost always is caused by tobacco smoking. It often starts in the bronchi, then quickly grows and spreads to other parts of the body, including the lymph nodes.
Other types of lung cancer
Less common types of lung cancer include:
- Carcinoid tumors
- Salivary gland carcinoma
- Some sarcomas
- Cancer of unknown primary
Cancer found in the lungs is sometimes another type of cancer that started somewhere else in the body and spread, or metastasized, to the lungs. These tumors are called lung metastases, and they are not the same as lung cancer. They usually are the primary, or original, type of cancer.
In rare cases, lung cancer can be passed down from one generation to the next. Genetic counseling may be right for you. Visit our genetic testing page to learn more.
Some people have an elevated risk of developing lung cancer. Review the lung cancer screening guidelines to see if you need to be tested.
Behavioral and lifestyle changes can help prevent lung cancer. Visit our prevention and screening section to learn how to manage your risk.
Lung Cancer Risk Factors
Anything that increases your chance of getting lung cancer is a risk factor. Smoking is the main risk factor for lung cancer.
- Smoking tobacco in cigarettes, cigars or pipes is responsible for 87% of lung cancer cases in the United States.
- The more years you smoke and the greater amount you smoke, the higher your risk of lung cancer.
- If you stop smoking, your risk of lung cancer becomes lower as time goes by.
- If you smoke and have other risk factors, your chance of getting lung cancer is higher.
- Read more about MD Anderson’s smoking cessation clinical trials
Other risk factors for lung cancer include:
- Family history of lung cancer
- Previous lung cancer
- Exposure to certain materials including radiation, arsenic, radon, chromium, nickel, soot, tar or asbestos
- Radiation therapy to the breast or chest
- Air pollution
- Secondhand smoke
- Lung diseases such as tuberculosis (TB)
Not everyone with risk factors develops lung cancer. However, if you have risk factors, it’s a good idea to discuss them with your doctor.