| Definition |
A group of diseases in which cells divide abnormally and without control, and spread to nearby tissues and other parts of the body. Without treatment, cancer can stop organs from working normally, damage body systems, and cause the patient to die. The main types of cancer include carcinoma (cancer that begins in the skin or in tissues that line or cover internal organs), sarcoma (cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue), leukemia (cancer that starts in the bone marrow and causes large numbers of abnormal blood cells to move into the bloodstream), and lymphoma and multiple myeloma (cancers that begin in the cells that protect the body against infection and disease). Cancer may be caused by multiple factors, such as radiation, sunlight, tobacco, certain viruses, and poisonous chemicals; however, the cause of many cancers is unknown. |