Cancer--A general term for a large group of diseases (more than 100), all characterized by uncontrolled growth and spread of abnormal cells. Cancer cells are abnormal and eventually form tumors that invade and destroy surrounding tissue; they may even spread via the Iymph system or bloodstream to distant areas of the body. (See Metastasis and Malignant Tumor)
Cancer Cell--A cell that divides and reproduces abnormally.
Cancer-Related Checkup--Periodic health examination for cancer in asymptomatic persons (without obvious signs or symptoms) in order to detect the disease at an early, curable stage.
Carcinogen--Any substance that initiates or promotes the development of cancer. For example, asbestos is a proven carcinogen.
Carcinoma--A form of cancer that develops in tissues covering or lining organs of the body, such as the skin, the uterus, the lung or the breast.
Carcinoma in Situ--An early stage in development, when the cancer is still confined to the tissues of origin. In situ carcinomas are highly curable.
Cell--The basic structural unit of life. All living matter is composed of cells.
Cervix--Any "necklike" structure; usually refers to the neck of the uterus where cancer may occur.
Chemoprevention--In cancer, this term is used to describe attempts at prevention of disease by drugs, chemicals, vitamins and/or minerals. The concept is under study but is not yet ready for wide application.
Chemotherapy--Treatment of disease, such as cancer, by drugs.
Clinical Trial--The scientific evaluation of the means to prevent, detect, diagnose or treat disease in human beings. Clinical trials are conducted after experiments in animals have shown evidence of potential effectiveness and preliminary studies in humans suggest usefulness.
Colon--The part of the large intestine that extends from the end of the small intestine to the rectum.
Colonoscopy--A technique used to visually examine the entire colon by means of a lighted, flexible instrument, called a fiber-optic colonoscope. This procedure may also obtain biopsy specimens of suspicious tissue.
Colostomy--A surgical procedure that creates an artificial opening in the abdominal wall for elimination of body wastes from the colon. It can be either temporary or permanent. Most colon cancers do not require colostomies if they are found early and treated promptly.
Combination Chemotherapy--Treatment consisting of the use of two or more chemicals to achieve the most effective results.
Combined Modality Therapy--Two or more types of treatment -- surgery, radiation therapy, chemotherapy or immunotherapy -- used alternatively or together for maximum effectiveness. For example, surgery for cancer is often followed by chemotherapy to destroy any random cancer cells that may have spread from the original site.
Computerized Tomography Scans--Commonly called CT scans, these specialized X-ray studies can find cancer or metastases. CT scans have revolutionized the diagnosis of cancer and other diseases.
Cyst--An abnormal saclike structure that contains liquid or semisolid material; may be benign or malignant. Lumps in the breast are often found to be harmless cysts and not cancer.
Cytology--Study of cells under a microscope. Cells that have been sloughed off or scraped off organs, such as the uterus, lungs, bladder or stomach, are microscopically examined for signs of cancer. Also called exfoliative cytology.