Changes in the structure of some of the many types of cells that make up the lungs may begin almost immediately upon exposure to carcinogens (cancercausing substances). Some of the thousands of chemicals contained in tobacco smoke—both inhaled directly and released into the air through secondhand smoke—are known respiratory carcinogens. Substances such as radon, asbestos, arsenic, uranium, and certain petroleum products also can cause lung cancer.
Regular exposure to any of these substances can damage individual cells in the lungs, causing them to multiply into an abnormal mass of cells called a tumor. The tumor can be benign, which means that it will not spread to other parts of the body and usually will not grow back if it is removed. If the tumor is malignant, however, it can invade and destroy surrounding tissue and may spread to other parts of the body through the bloodstream, causing new tumors (called metastases) to form in other tissues. And because all blood flows through the lungs, cancer that begins elsewhere in the body may spread to the lungs.
A tumor in one of the bronchi can irritate the lining of the airway and cause a persistent cough, which may cause the tumor to bleed. As it grows, the tumor may block the airway, resulting in repeated bouts of pneumonia or other respiratory infections. A tumor located in the outer part of a lung may not produce any symptoms until it is large enough to press against the chest wall and cause pain. If you experience any of the warning signs of lung cancer (see Post Warning Sings of Lung Cancer), see your doctor as soon as possible.
Tests for lung cancer include a chest X ray, a microscopic examination of mucus expelled from your lungs, and a computed tomography (CT) scan or magnetic resonance imaging (MRI) of your chest. If something resembling a tumor is seen on an X ray or a scan, your doctor may perform a bronchoscopy and a biopsy (removal of a small piece of tissue from the suspected tumor for examination under a microscope). Depending on the results, other tests and procedures may be performed to identify the type of cancer and the extent to which it has spread.
Two major types of cancer begin in the lungs. Non-small cell lung cancer generally grows and spreads slowly. This form of cancer accounts for about three fourths of all cases of lung cancer. The non-small cell cancers include squamous cell carcinoma, adenocarcinoma, and large cell carcinoma. The less common small cell lung cancer (sometimes called oat cell cancer) grows quickly and is more likely to spread to other parts of the body, such as the lymph nodes, brain, liver, and bones.
Treatment of lung cancer depends on the type of cancer cell involved, the size and location of the primary (or first) tumor, and the size and location of any secondary tumors (tumors that have spread from the primary tumor to another part of the body). Treatment options include surgical removal of the lung tumor, use of anticancer drugs (chemotherapy), use of radiation (radiation therapy), use of lasers (photodynamic therapy), or a combination of these treatments.
Although treatment is improving, the outlook for lung cancer is generally poor. If you smoke or are exposed to any known carcinogens, you should immediately take steps to prevent lung cancer.