Cancer InDepth: Lung Cancer
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Lung cancer is a disease in which cancer cells grow in the lungs.
The lungs are the organs responsible for bringing oxygen into the body and expelling carbon dioxide. The right lung has three lobes, the left lung has two. Air enters the lungs through the trachea, or windpipe. Tubes called bronchi branch off from the trachea and then divide into smaller tubes called bronchioles. The bronchioles connect to tiny air sacs, called alveoli. Many tiny blood vessels pass through the alveoli, where the exchange of gases takes place.
Lung cancer occurs when cells in the lung divide without control or order. Normally, cells divide in a regulated manner. If cells keep dividing uncontrollably when new cells are not needed, a mass of tissue forms, called a growth or tumor. The term cancer refers to malignant tumors, which can invade nearby tissues and can spread to other parts of the body. A benign tumor does not invade or spread.
Lung cancers develop anywhere in the contents of the chest, particularly in the lung itself, its bronchi, or alveoli. Tumors may take years to develop.
Lung cancers that start in the lungs are divided into two general types:
Non-small cell lung cancer – generally grows and spreads slowly. This accounts for about 80% of the lung cancers diagnosed each year in the United States. The three subtypes of non-small cell lung cancer are squamous cell carcinoma, adenocarcinoma, and large-cell undifferentiated carcinoma.
Small cell lung cancer – generally grows more quickly and is more likely to spread to other parts of the body. This accounts for about 20% of the lung cancers diagnosed each year. Other names for this disease include oat cell carcinoma and small cell undifferentiated carcinoma.
Who is Affected
More Americans, men and women, die of lung cancer than any other cancer—about 154,900 people will die annually, which is more than die from colon, breast, and prostate cancer combined, according to the American Cancer Society. The five-year survival rate for all stages of non-small cell lung cancer is 16%; for small cell lung cancer it is 6%. Most people are diagnosed with lung cancer after it has spread to the lymph nodes or other organs, decreasing the odds of survival.
This year, about 169,400 Americans will learn they have lung cancer. About 13% of all new cancers are lung cancer. The average age of people diagnosed with the disease is 60. It can take years to develop and is rarely found in people under age 40.
Causes and Complications
Lung cancer is caused by exposure to cancer-causing substances. Most cases are associated with tobacco use. Causative agents include:
- First- or second-hand cigarette smoke
- Pipe or cigar smoking
- Radon – an invisible, odorless, and tasteless radioactive gas in soil and rocks
- Asbestos – a group of minerals that occur naturally as fibers and are used in certain industries
- Air pollutants
Complications of lung cancer occur when the tumor presses against other structures. If the tumor pushes against the windpipe it can block the flow of oxygen and carbon dioxide. If it compresses the superior vena cava, a major vein connecting to the heart, fluid will back up resulting in swelling in the face, neck, and arms. Other symptoms include shortness of breath and headache.
This report covers the following:
American Cancer Society
American Lung Association
Bast R. Cancer Medicine e5 . Hamilton, Ontario: B.C. Decker Inc.; 2000
National Cancer Institute
Last reviewed February 2003 by
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