C-erbB-2: The gene that controls cell growth by making the human epidermal growth factor receptor 2. Also called HER2/neu.

C-kit receptor: A protein on the surface of some cells that binds to stem cell factor (a substance that causes certain types of cells to grow). Altered forms of this receptor may be associated with some types of cancer.

CA-125: Substance sometimes found in an increased amount in the blood, other body fluids, or tissues and that may suggest the presence of some types of cancer.

Cachexia: The loss of body weight and muscle mass frequently seen in patients with cancer, AIDS, or other diseases.

Calcification: Deposits of calcium in the tissues of the breast. Calcification in the breast can be seen on a mammogram, but cannot be detected by touch. There are two types of breast calcification, macrocalcification and microcalcification. Macrocalcifications are large deposits and are usually not related to cancer. Microcalcifications are specks of calcium that may be found in an area of rapidly dividing cells. Many microcalcifications clustered together may be a sign of cancer.

Calcitonin: A hormone secreted by the thyroid that lowers blood calcium levels.

Calcitriol (kal-sih-TREE-ol): Calcitriol is a form of vitamin D that is used to treat and prevent low levels of calcium in the blood of patients whose kidneys or parathyroid glands (glands in the neck that release natural substances to control the amount of calcium in the blood) are not working normally. Low blood levels of calcium may cause bone disease. Calcitriol is in a class of medications called vitamins. It works by helping the body to use more of the calcium found in foods or supplements.

Calcium (KAL-see-um): A mineral found in teeth, bones, and other body tissues.

Calcium carbonate: A mineral taken primarily as a supplement to prevent osteoporosis. It is also being studied for cancer prevention.

Caloric intake: Refers to the number of calories (energy content) consumed.

Campath-1H: A monoclonal antibody used to treat leukemia. Monoclonal antibodies are made in the laboratory. They can find cancer cells and bind to them.

Camphor: A substance that comes from the wood and bark of the camphor tree or is made in the laboratory. It has a very unique smell and taste and is used in commercial products (for example, mothballs). Camphor is used in topical anti-infective and anti-pruritic (anti-itching) agents.

Camptothecin: An anticancer drug that belongs to the family of drugs called topoisomerase inhibitors.

Camptothecin analogue: An anticancer drug related in structure to camptothecin, a topoisomerase inhibitor. One such drug is aminocamptothecin.

Cancer: A term for diseases in which abnormal cells divide without control. Cancer cells can invade nearby tissues and can spread through the bloodstream and lymphatic system to other parts of the body.

Cancer of unknown primary origin: Cancer cells are found in the body, but the place where the cells first started growing (the origin or primary site) cannot be determined.

Cancer vaccine: A vaccine designed to prevent or treat cancer.

Capecitabine: An anticancer drug that belongs to the family of drugs called antimetabolites.

Capsaicin: A component of certain plants, including cayenne and red pepper, used topically for peripheral nerve pain. Also being studied for controlling mucositis pain after chemotherapy and radiation therapy.

Captopril: A drug used to lower high blood pressure. It belongs to the family of drugs called ACE inhibitors.

Carbendazim: An anticancer drug that belongs to the family of drugs called antifungal agents.

Carbogen: An inhalant of oxygen and carbon dioxide that increases the sensitivity of tumor cells to the effects of radiation therapy.

Carboplatin: An anticancer drug that belongs to the family of drugs called platinum compounds.

Carboplatin: An anticancer drug that belongs to the family of drugs called platinum compounds.

Carboxyamidotriazole: An anticancer drug that belongs to the family of drugs called angiogenesis inhibitors.

Carboxypeptidase-G2: A bacterial enzyme that belongs to the family of drugs called chemoprotective agents. It is used to neutralize the toxic effects of methotrexate.

Carcinoembryonic antigen peptide-1: CAP-1. A protein that can stimulate an immune response to certain tumors.