Non-small cell lung cancer is a type of 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. Two tubes called bronchi lead from the trachea (windpipe) to the right and left lungs. Lung cancer may also form in the bronchi. Tiny air sacs called alveoli and small tubes called bronchioles make up the inside of the lungs.

A thin membrane called the pleura covers the outside of each lung and lines the inside wall of the chest cavity. This creates a sac called the pleural cavity. The pleural cavity normally contains a small amount of fluid that helps the lungs move smoothly in the chest when you breathe.

There are two main types of lung cancer: non-small cell lung cancer and small cell lung cancer. Non-small cell lung cancer is more common than small cell lung cancer.

There are several types of non-small cell lung cancer.

Each type of non-small cell lung cancer has different kinds of cancer cells. The cancer cells of each type grow and spread in different ways. The types of non-small cell lung cancer are named for the kinds of cells found in the cancer and how the cells look under a microscope:

• Squamous cell carcinoma is a type of lung cancer that forms in the thin, flat cells lining the inside of the lungs. This is also called epidermoid carcinoma.
• Large cell carcinoma is a type of lung cancer that may begin in several types of large cells.
• Adenocarcinoma is a type of lung cancer that begins in the cells that line the alveoli and make substances such as mucus.

Less common types of non-small cell lung cancer include adenosquamous carcinoma, sarcomatoid carcinoma, salivary gland carcinoma, carcinoid tumor, and unclassified carcinoma.

Smoking is the major risk factor for non-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 non-small cell lung cancer include coughing and shortness of breath.

Sometimes lung cancer does not cause any signs or symptoms. It may be found during a chest x-ray done for another condition. Signs and symptoms may be caused by 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
• loss of appetite
• weight loss for no known reason
• fatigue
• trouble swallowing
• swelling in the face and/or veins in the neck

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

Non-small cell lung cancer is usually diagnosed with tests and procedures that make pictures of the lung and the area around it. The process used to find out if cancer cells have spread within and around the lung is called staging. Tests and procedures to detect, diagnose, and stage non-small cell lung cancer are usually done at the same time. To plan treatment, it is important to know the stage of the disease and whether the cancer can be removed by surgery.

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.

If lung cancer is suspected, you will have a biopsy.

You may have one of the following types of biopsies:

• 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 locate 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.

  An endoscopic ultrasound (EUS) is a type of ultrasound that may be used to guide an FNA biopsy of the lung, lymph nodes, or other areas. EUS is a procedure in which an endoscope is inserted into the body. An endoscope is a thin, tube-like instrument with a light and a lens for viewing. A probe at the end of the endoscope is used to bounce high-energy sound waves (ultrasound) off internal tissues or organs and make echoes. The echoes form a picture of body tissues called a sonogram.

  
• 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.
• Anterior mediastinotomy is a surgical procedure to look at the organs and tissues between the lungs and between the breastbone and heart for abnormal areas. An incision (cut) is made next to 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. This is also called the Chamberlain procedure.
• Lymph node biopsy is the removal of all or part of a lymph node. A pathologist views the lymph node tissue under a microscope to check for cancer cells. A lymph node biopsy may be done at the same time as other types of biopsies.

One or more of the following laboratory tests may be done to study the tissue from the biopsy:

• Molecular tests check for certain genes, proteins, or other molecules in a sample of tissue, blood, or other body fluid. Molecular tests check for certain gene or chromosome changes that occur in non-small cell lung cancer.
• Immunohistochemistry 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 non-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 non-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 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.
• Pulmonary function test (PFT) checks how well the lungs are working. It measures how much air the lungs can hold and how quickly air moves into and out of the lungs. It also measures how much oxygen is used and how much carbon dioxide is given off during breathing. This is also called lung function test.
• Bone marrow aspiration and biopsy is the removal of bone marrow, blood, and a small piece of bone by inserting a hollow needle into the hipbone or breastbone. A pathologist views the bone marrow, blood, and bone under a microscope to look for signs of cancer.

Some people decide to get a second opinion.

You may want to get a second opinion to confirm your non-small cell lung 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 (the size of the tumor and whether it is in the lung only or has spread to other places in the body)
• the type of lung cancer
• whether the cancer has mutations (changes) in certain genes, such as the epidermal growth factor receptor (EGFR) gene or the anaplastic lymphoma kinase (ALK) gene
• whether there are signs and symptoms such as coughing or trouble breathing
• your general health

For most people with non-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 or quality of life. Clinical trials are taking place in most parts of the country for people with all stages of non-small cell lung cancer. Information about ongoing clinical trials is available at Clinical Trials Information for Patients and Caregivers.