Lung cancer is cancer that forms in tissues of the lung, usually in the cells lining air passages. The two main types are small cell lung cancer and non-small cell lung cancer. These types are diagnosed based on how the cells look under a microscope. Each type of lung cancer grows and spreads in different ways and is treated differently.

 

Non-small cell lung cancer. This is more common than small cell lung cancer, and generally grows and spreads more slowly. There are three main types of non-small cell lung cancer, named for the type of cells in which the cancer develops: squamous cell carcinoma (also called epidermoid carcinoma), adenocarcinoma, and large cell carcinoma.

Small cell lung cancer. This is sometimes called oat cell cancer, and is less common than non-small cell lung cancer. Small cell lung cancer grows more quickly and is more likely to spread to other organs in the body.

 

The lungs

The lungs, a pair of sponge-like, cone-shaped organs, are part of the respiratory system. The right lung has three sections, called lobes; it is a little larger than the left lung, which has two lobes. When we breathe in, the lungs take in oxygen, which our cells need to live and carry out their normal functions. When we breathe out, the lungs get rid of carbon dioxide, which is a waste product of the body's cells.

 

Who is at risk?

Researchers have discovered several causes of lung cancer – most related to the use of tobacco.

 

Cigarettes. Smoking cigarettes causes lung cancer. Harmful substances, called carcinogens, in tobacco damage the cells in the lungs. Over time, the damaged cells may become cancerous. The likelihood that a smoker will develop lung cancer is affected by the age at which smoking began, how long the person has smoked, the number of cigarettes smoked per day, and how deeply the smoker inhales. Stopping smoking greatly reduces a person's risk for developing lung cancer.

Cigars and pipes. Cigar and pipe smokers have a higher risk of lung cancer than nonsmokers. The number of years a person smokes, the number of pipes or cigars smoked per day, and how deeply the person inhales all affect the risk of developing lung cancer. Even cigar and pipe smokers who do not inhale are at increased risk for lung, mouth, and other types of cancer.

Environmental tobacco smoke. The chance of developing lung cancer is increased by exposure to environmental tobacco smoke (ETS) – the smoke in the air when someone else smokes. Exposure to ETS, or secondhand smoke, is called involuntary or passive smoking.

Radon. Radon is an invisible, odorless, and tasteless radioactive gas that occurs naturally in soil and rocks. It can cause damage to the lungs that may lead to lung cancer. People who work in mines may be exposed to radon and, in some parts of the country, radon is found in houses. Smoking increases the risk of lung cancer even more for those already at risk because of exposure to radon. A kit available at most hardware stores allows homeowners to measure radon levels in their homes. The home radon test is relatively easy to use and inexpensive. Once a radon problem is corrected, the hazard is gone for good.

Asbestos. Asbestos is the name of a group of minerals that occur naturally as fibers and are used in certain industries. Asbestos fibers tend to break easily into particles that can float in the air and stick to clothes. When the particles are inhaled, they can lodge in the lungs, damaging cells and increasing the risk for lung cancer. Studies have shown that workers who have been exposed to large amounts of asbestos have a risk of developing lung cancer that is 3 to 4 times greater than that for workers who have not been exposed to asbestos. This exposure has been observed in such industries as shipbuilding, asbestos mining and manufacturing, insulation work, and brake repair. The risk of lung cancer is even higher among asbestos workers who also smoke. Asbestos workers should use the protective equipment provided by their employers and follow recommended work practices and safety procedures. Anyone who contracted mesothelioma from asbestos exposure should contact an experienced attorney immediately.

Pollution. Researchers have found a link between lung cancer and exposure to certain air pollutants, such as by-products of the combustion of diesel and other fossil fuels. However, this relationship has not been clearly defined, and more research is being done.

Lung diseases. Certain lung diseases, such as tuberculosis (TB), increase a person's chance of developing lung cancer. Lung cancer tends to develop in areas of the lung that are scarred from TB.

Personal history. A person who has had lung cancer once is more likely to develop a second lung cancer compared with a person who has never had lung cancer. Quitting smoking after lung cancer is diagnosed may prevent the development of a second lung cancer.

 

Researchers continue to study the causes of lung cancer and to search for ways to prevent it. We already know that the best way to prevent lung cancer is to quit (or never start) smoking. The sooner a person quits smoking the better. Even if you have been smoking for many years, it's never too late to benefit from quitting.

 

Signs and symptoms

Common signs and symptoms of lung cancer include:

 

A cough that doesn't go away and gets worse over time

Constant chest pain

Coughing up blood

Shortness of breath, wheezing, or hoarseness

Repeated problems with pneumonia or bronchitis

Swelling of the neck and face

Loss of appetite or weight loss

Fatigue

 

These symptoms may be caused by lung cancer or by other conditions. It is important to check with a doctor.

 

Diagnosis

To help find the cause of symptoms, the doctor evaluates a person's medical history, smoking history, exposure to environmental and occupational substances, and family history of cancer. The doctor also performs a physical exam and may order a chest X-ray and other tests. If lung cancer is suspected, sputum cytology (the microscopic examination of cells obtained from a deep-cough sample of mucus in the lungs) is a simple test that may be useful in detecting lung cancer. To confirm the presence of lung cancer, the doctor must examine tissue from the lung. A biopsy – the removal of a small sample of tissue for examination under a microscope by a pathologist – can show whether a person has cancer. A number of procedures may be used to obtain this tissue:

 

Bronchoscopy. The doctor puts a bronchoscope (a thin, lighted tube) into the mouth or nose and down through the windpipe to look into the breathing passages. Through this tube, the doctor can collect cells or small samples of tissue.

Needle aspiration. A needle is inserted through the chest into the tumor to remove a sample of tissue.

Thoracentesis. Using a needle, the doctor removes a sample of the fluid that surrounds the lungs to check for cancer cells.

Thoracotomy. Surgery to open the chest is sometimes needed to diagnose lung cancer. This procedure is a major operation performed in a hospital.

 

Staging

If the diagnosis is cancer, the doctor will want to learn the stage (or extent) of the disease. Staging is done to find out whether the cancer has spread and, if so, to what parts of the body. Lung cancer often spreads to the brain or bones. Knowing the stage of the disease helps the doctor plan treatment. Some tests used to determine whether the cancer has spread include:

 

CAT (or CT) scan (computed tomography). A computer linked to an X-ray machine creates a series of detailed pictures of areas inside the body.

MRI (magnetic resonance imaging). A powerful magnet linked to a computer makes detailed pictures of areas inside the body.

Radionuclide scanning. Scanning can show whether cancer has spread to other organs, such as the liver. The patient swallows or receives an injection of a mildly radioactive substance. A machine (scanner) measures and records the level of radioactivity in certain organs to reveal abnormal areas.

Bone scan. A bone scan, one type of radionuclide scanning, can show whether cancer has spread to the bones. A small amount of radioactive substance is injected into a vein. It travels through the bloodstream and collects in areas of abnormal bone growth. An instrument called a scanner measures the radioactivity levels in these areas and records them on X-ray film.

Mediastinoscopy/mediastinotomy. A mediastinoscopy can help show whether the cancer has spread to the lymph nodes in the chest. Using a lighted viewing instrument, called a scope, the doctor examines the center of the chest (mediastinum) and nearby lymph nodes. In mediastinoscopy, the scope is inserted through a small incision in the neck; in mediastinotomy, the incision is made in the chest. In either procedure, the scope is also used to remove a tissue sample. The patient receives a general anesthetic.

 

Treatment

Read about how lung cancer is treated.