| What
is Cancer?
Cancer is a group of more than 100 different diseases. Cancer occurs when cells become abnormal and keep dividing and forming more cells, without the usual control or order of the body. All organs of the body are made up of cell. Normally, cells divide to produce more cells only when the body needs them, such as to repair damage or replace old cells which have died. This orderly process helps to keep us healthy. If cells keep dividing when new cells are not needed, a mass of tissue forms. This mass of extra tissue, called a growth or tumor, can be either benign or malignant. Benign tumors are not cancer. They can usually be removed and, in most cases, they do not grow back. Most important, cells from benign tumors do not invade and spread to other parts of the body. Benign tumors are rarely life-threatening. Malignant tumors are cancer. Cancer cell can invade other tissues and damage nearby tissues and organs. Also, cancer cells can break away from a malignant tumor and spread to other organs by way of the lymphatic system or bloodstream. The spread of cancer cells to other organs is called metastasis. Most cancers are named for the type of cell or organ in which they begin. When cancer spreads, the new tumor has the same kind of abnormal cells and the same name as the primary tumor. For example, if lung cancer spreads to the liver, the cancer cells in the liver are still lung cancer cells (not liver cancer). The disease is called metastatic lung cancer. What Causes Cancer to Form? Cancer develops gradually as a result of injury to cells, from a complex mix of factors related to the environment, lifestyle, and genetics (inherited traits). Scientists have identified many risk factors that increase the chances of developing cancer. They estimate that about 80 percent of all cancers are related to the use of tobacco products (smoking and smokeless types), to what we eat and drink, and, to a lesser extent, to exposure to radiation and cancer-causing chemicals (carcinogens) in the environment and the workplace. Some people are more sensitive to these factors than others. Additional general information about cancer and its causes can be obtained by contacting the National Cancer Institute (1-800-4CANCER), the American Cancer Society, and the Leukemia Society of America.
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