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. The bronchi are sometimes also involved in lung cancer. Tiny air sacs called alveoli and small tubes called bronchioles make up the inside of the lungs.
Anatomy of the respiratory system, showing the trachea and both lungs and their lobes and airways. Lymph nodes and the diaphragm are also shown. Oxygen is inhaled into the lungs and passes through the thin membranes of the alveoli and into the bloodstream (see inset).
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.
See the following PDQ summaries for more information about lung cancer:
- Small Cell Lung Cancer Treatment
- Unusual Cancers of Childhood
- Lung Cancer Prevention
- Lung Cancer Screening
- Smoking in Cancer Care
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: Cancer that begins in squamous cells, which are thin, flat cells that look like fish scales. This is also called epidermoid carcinoma.
- Large cell carcinoma: Cancer that may begin in several types of large cells.
- Adenocarcinoma: Cancer that begins in the cells that line the alveoli and make substances such as mucus.
Other less common types of non-small cell lung cancer are: pleomorphic, carcinoid tumor, salivary gland carcinoma, and unclassified carcinoma.
Smoking increases the risk of non-small cell lung cancer.
Smoking cigarettes, pipes, or cigars is the most common cause 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. If a person has stopped smoking, the risk becomes lower as the years pass.
Anything that increases your chance of getting a disease is called a risk factor. Having a risk factor does not mean that you will get cancer; not having risk factors doesn't mean that you will not get cancer. Talk with your doctor if you think you may be at risk.
Risk factors for lung cancer include the following:
- Smoking cigarettes, pipes, or cigars, now or in the past.
- Being exposed to secondhand smoke.
- Having a family history of lung cancer.
- Being treated with radiation therapy to the breast or chest.
- Being exposed to asbestos, chromium, nickel, arsenic, soot, or tar in the workplace.
- Being exposed to radon in the home or workplace.
- Living where there is air pollution.
- Being infected with the human immunodeficiency virus (HIV).
- Using beta carotene supplements and being a heavy smoker.
When smoking is combined with other risk factors, the risk of lung cancer is increased.
Signs of non-small cell lung cancer include a cough that doesn't go away 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 any of the following:
- Chest discomfort or pain.
- A cough that doesn't go away or gets worse over time.
- Trouble breathing.
- Blood in sputum (mucus coughed up from the lungs).
- Loss of appetite.
- Weight loss for no known reason.
- Feeling very tired.
- Trouble swallowing.
- Swelling in the face and/or veins in the neck.
Tests that examine the lungs are used to detect (find), diagnose, and stage non-small cell lung cancer.
Tests and procedures to detect, diagnose, and stage non-small cell lung cancer are often done at the same time. Some of the following tests and procedures may be used:
- Physical exam and history: An exam of the body to check general signs of health, including checking for signs of disease, such as lumps or anything else that seems unusual. A history of the patient's health habits, including smoking, and past jobs, illnesses, and treatments will also be taken.
- Laboratory tests: 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: An x-ray of the organs and bones inside the chest. An x-ray is a type of energy beam that can go through the body and onto film, making a picture of areas inside the body.
X-ray of the chest. X-rays are used to take pictures of organs and bones of the chest. X-rays pass through the patient onto film.
- CT scan (CAT scan): A procedure that makes a series of detailed pictures of areas inside the body, such as the chest, taken from different angles. The pictures are made by a computer linked to an x-ray machine. 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 : A procedure in which a pathologist views a sample of sputum (mucus coughed up from the lungs) under a microscope, to check for cancer cells.
Fine-needle aspiration (FNA) biopsy of the lung: 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.
Fine-Needle Aspiration Biopsy of the Lung. The patient lies on a table that slides through the computed tomography (CT) machine, which takes x-ray pictures of the inside of the body. The x-ray pictures help the doctor see where the abnormal tissue is in the lung. A biopsy needle is inserted through the chest wall and into the area of abnormal lung tissue. A small piece of tissue is removed through the needle and checked under the microscope for signs of cancer.
: 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.
Bronchoscopy. A bronchoscope is inserted through the mouth, trachea, and major bronchi into the lung, to look for abnormal areas. A bronchoscope is a thin, tube-like instrument with a light and a lens for viewing. It may also have a cutting tool. Tissue samples may be taken to be checked under a microscope for signs of disease.
- Thoracoscopy: 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 : 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.
- Light and electron microscopy: 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: A test that uses antibodies to check for certain antigens in a sample of tissue. The antibody is usually linked to a radioactive substance or a dye that causes the tissue to light up under a microscope. This type of test may be used to tell the difference between different types of cancer.
Certain factors affect prognosis (chance of recovery) and treatment options.
The prognosis (chance of recovery) and treatment options depend on the following:
- 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.
- The patient's general health.
For most patients with non-small cell lung cancer, current treatments do not cure the cancer.
If lung cancer is found, taking part in one of the many clinical trials being done to improve treatment should be considered. Clinical trials are taking place in most parts of the country for patients with all stages of non-small cell lung cancer. Information about ongoing clinical trials is available from the NCI Web site.