Multiple: Cancer
Multiple: Cancer
Cancer is a group of diseases rather than a single disorder. All cancers have three characteristics in common, however. First, they are diseases in which a group of cells begins to grow uncontrollably. Second, the uncontrolled cell growth invades and harms other tissues nearby. Third, cancers metastisize—that is, they spread to other tissues or organs through the lymphatic system or bloodstream. A group of cells can sometimes form a tumor (swelling) that is not cancerous. These benign tumors do not invade other tissues and they do not metastasize but can cause significant illness if growing in a vital area.
Cancer can affect people in any age group; however, the risk for most cancers increases as people get older. Although the diagnosis and treatment of cancer continues to improve, cancers are still responsible for 25 percent of all deaths in the United States and other developed countries. About 7.7 million people die of cancer each year worldwide.
Most cancers are caused by changes in the genetic material of the cells that are multiplying abnormally. These changes may be the result of inherited genetic defects or of such factors as radiation, hormonal imbalances, infectious diseases, or exposure to tobacco smoke and other dangerous chemicals.
SEE ALSO Brain tumors; Breast cancer; Colorectal cancer; Hodgkin disease; Leukemia; Lung cancer; Lymphoma; Prostate cancer; Skin cancer