Although all cancers have similar characteristics, each is different in its own way. For years, researchers have been trying to determine what causes cancer. According to recent discoveries, cancer is the result of changes in genes in the body. Usually both types work in balance so that healthy cells can divide and replace dead or defective cells. In cancer, abnormal cells grow out of control.
Many factors can influence a person's risk for cancer.
Heredity accounts for about 10 percent of all cancers. Viruses may cause certain leukemias and lymphomas, cancer of the nose and pharynx, liver cancer, and cervical cancer. It also is thought that about 5 percent of all cancers might be caused by radiation, including medical, occupational, and environmental exposures. Many chemicals used in industry also are carcinogens. Smoking, excessive exposure to sun, over use of alcohol, and a high-fat diet also can increase the risk of developing some types of cancer.