Small cell lung cancer is a type of fast-growing cancer that forms in the tissues of the lung.

The lungs are a pair of cone-shaped breathing organs in the chest. The lungs bring oxygen into the body as you breathe in. They release carbon dioxide, a waste product of the body's cells, as you breathe out. Each lung has sections called lobes. The left lung has two lobes. The right lung is slightly larger and has three lobes. A thin membrane called the pleura surrounds the lungs. Two tubes called bronchi lead from the trachea (windpipe) to the right and left lungs. Lung cancer may also form in the bronchi. Small tubes called bronchioles and tiny air sacs called alveoli make up the inside of the lungs.

There are two types of lung cancer: small cell lung cancer and non-small cell lung cancer. Small cell lung cancer is less common than non-small cell lung cancer.

There are two main types of small cell lung cancer.

The cancer cells of each type grow and spread in different ways. 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. The cancer cells of each type grow and spread in different ways:

• Small cell carcinoma (also called oat cell cancer) is a type of lung cancer that can grow and spread quickly, often leading to the cancer spreading to other parts of the body early in the disease process. This is the most common type of small cell lung cancer.
• Combined small cell carcinoma is a rare subtype of lung cancer that has characteristics of small cell lung cancer and non-small cell lung cancer in the same tumor.

Smoking is the major risk factor for small cell lung cancer.

Lung cancer is caused by certain changes to the way lung cells function, especially how they grow and divide into new cells. There are many risk factors for lung cancer, but many do not directly cause cancer. Instead, they increase the chance of DNA damage in cells that may lead to lung cancer. Learn more about how cancer develops at What Is Cancer?

A risk factor is anything that increases the chance of getting a disease. Some risk factors for lung cancer, like smoking, can be changed. However, risk factors also include things you cannot change, like your genetics, age, and family history. Learning about risk factors for lung cancer can help you make changes that might lower your risk of getting it.

Smoking tobacco now or in the past is the most important risk factor for lung cancer. Smoking cigarettes, pipes, or cigars increases the risk of lung cancer. The earlier in life a person starts smoking, the more often a person smokes, and the more years a person smokes, the greater the risk of lung cancer.

Other risk factors for lung cancer include:

• being exposed to secondhand smoke
• being exposed to asbestos, arsenic, chromium, beryllium, nickel, soot, or tar in the workplace
• being exposed to radiation from:
  • radiation therapy to the breast or chest
  • radon in the home or workplace
  • imaging tests such as CT scans
  • atomic bomb radiation
• living where there is air pollution
• having a family history of lung cancer
• being infected with HIV
• taking beta carotene supplements and being a heavy smoker

Older age is the main risk factor for most cancers. The chance of getting cancer increases as you get older.

Having one or more of these risk factors does not necessarily mean you will get lung cancer. Many people with risk factors never develop lung cancer, whereas others with no known risk factors do. Talk with your doctor if you think you might be at increased risk.

When smoking is combined with other risk factors, the risk of lung cancer is increased.

Signs and symptoms of small cell lung cancer include coughing and shortness of breath.

These and other signs and symptoms may be caused by small cell lung cancer or by other conditions. Check with your doctor if you have:

• chest discomfort or pain
• 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
• trouble swallowing
• loss of appetite
• weight loss for no known reason
• feeling very tired
• swelling in the face and/or veins in the neck

Tests and procedures that examine the lungs are used to diagnose and stage small cell lung cancer.

In addition to asking about your personal and family health history and doing a physical exam, your doctor may perform the following tests and procedures:

• Laboratory tests are medical procedures that test samples of tissue, blood, urine, or other substances in the body. These tests help to diagnose disease, plan and check treatment, or monitor the disease over time.
• Chest x-ray is a type of radiation that can go through the body and make pictures of the organs and bones inside the chest.
• CT scan (CAT scan) of the brain, chest, and abdomen uses a computer linked to an x-ray machine to make a series of detailed pictures of areas inside the body. The pictures are taken from different angles and are used to create 3-D views of tissues and organs. A dye may be injected into a vein or swallowed to help the organs or tissues show up more clearly. This procedure is also called computed tomography, computerized tomography, or computerized axial tomography.
• Sputum cytology uses a microscope to check for cancer cells in the sputum (mucus coughed up from the lungs).
• Biopsy is the removal of cells or tissues so they can be viewed under a microscope by a pathologist to check for signs of cancer. The different ways a biopsy can be done include the following:
  • Fine-needle aspiration (FNA) biopsy of the lung is the removal of tissue or fluid from the lung, using a thin needle. A CT scan, ultrasound, or other imaging procedure is used to find the abnormal tissue or fluid in the lung. A small incision may be made in the skin where the biopsy needle is inserted into the abnormal tissue or fluid. A sample is removed with the needle and sent to the laboratory. A pathologist then views the sample under a microscope to look for cancer cells. A chest x-ray is done after the procedure to make sure no air is leaking from the lung into the chest.
  • Bronchoscopy is a procedure to look inside the trachea and large airways in the lung for abnormal areas. A bronchoscope is inserted through the nose or mouth into the trachea and lungs. A bronchoscope is a thin, tube-like instrument with a light and a lens for viewing. It may also have a tool to remove tissue samples, which are checked under a microscope for signs of cancer.
  • Thoracoscopy is a surgical procedure to look at the organs inside the chest to check for abnormal areas. An incision (cut) is made between two ribs, and a thoracoscope is inserted into the chest. A thoracoscope is a thin, tube-like instrument with a light and a lens for viewing. It may also have a tool to remove tissue or lymph node samples, which are checked under a microscope for signs of cancer. In some cases, this procedure is used to remove part of the esophagus or lung. If certain tissues, organs, or lymph nodes can’t be reached, a thoracotomy may be done. In this procedure, a larger incision is made between the ribs and the chest is opened.
  • Thoracentesis is the removal of fluid from the space between the lining of the chest and the lung, using a needle. A pathologist views the fluid under a microscope to look for cancer cells.
  • Mediastinoscopy is a surgical procedure to look at the organs, tissues, and lymph nodes between the lungs for abnormal areas. An incision (cut) is made at the top of the breastbone and a mediastinoscope is inserted into the chest. A mediastinoscope is a thin, tube-like instrument with a light and a lens for viewing. It may also have a tool to remove tissue or lymph node samples, which are checked under a microscope for signs of cancer.
• Light and electron microscopy is a laboratory test in which cells in a sample of tissue are viewed under regular and high-powered microscopes to look for certain changes in the cells.
• Immunohistochemistry is a laboratory test that uses antibodies to check for certain antigens (markers) in a sample of a patient’s tissue. The antibodies are usually linked to an enzyme or a fluorescent dye. After the antibodies bind to a specific antigen in the tissue sample, the enzyme or dye is activated, and the antigen can then be seen under a microscope. This type of test is used to help diagnose cancer and to help tell one type of cancer from another type of cancer.

After small cell lung cancer has been diagnosed, tests are done to find out if cancer cells have spread within the chest or to other parts of the body.

The process used to find out if cancer has spread within the chest or to other parts of the body is called staging. The information gathered from the staging process determines the stage of the disease. It is important to know the stage in order to plan treatment. Some of the tests used to diagnose small cell lung cancer are also used to stage the disease.

Imaging tests that may be used in the staging process include:

• MRI (magnetic resonance imaging) of the brain uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas inside the brain. This procedure is also called nuclear magnetic resonance imaging (NMRI).
• PET scan (positron emission tomography scan) uses a small amount of radioactive sugar (also called glucose) that is injected into a vein. Then a scanner rotates around the body to make detailed, computerized pictures of areas inside the body where the glucose is taken up. Because cancer cells often take up more glucose than normal cells, the pictures can be used to find cancer cells in the body. A PET scan and CT scan may be done at the same time. This is called a PET-CT.
• Bone scan checks for rapidly dividing cells, such as cancer cells, in the bone. A very small amount of radioactive material is injected into a vein and travels through the bloodstream. The radioactive material collects in the bones with cancer and is detected by a scanner.

Some people decide to get a second opinion.

You may want to get a second opinion to confirm your cancer diagnosis and treatment plan. If you seek a second opinion, you will need to get medical test results and reports from the first doctor to share with the second doctor. The second doctor will review the pathology report, slides, and scans. They may agree with the first doctor, suggest changes or another treatment approach, or provide more information about your cancer.

To learn more about choosing a doctor and getting a second opinion, see Finding Cancer Care. You can contact NCI’s Cancer Information Service via chat, email, or phone (both in English and Spanish) for help finding a doctor, hospital, or getting a second opinion. For questions you might want to ask at your appointments, see Questions to Ask Your Doctor about Cancer.

Certain factors affect prognosis (chance of recovery) and treatment options.

The prognosis and treatment options depend on:

• the stage of the cancer (whether it is in the chest cavity only or has spread to other places in the body)
• the patient’s age, gender, and general health

For certain patients, prognosis also depends on whether the patient is treated with both chemotherapy and radiation.

For most people with small cell lung cancer, current treatments do not cure the cancer. If lung cancer is found, you may want to think about taking part in one of the many clinical trials being done to improve treatment. Clinical trials are taking place in most parts of the country for patients with all stages of small cell lung cancer. Information about ongoing clinical trials is available from the NCI website.