The following glossary was modified from the glossary on the National Cancer Institute's Web site, available from http://www.nci.nih.gov.

acute lymphocytic leukemia: Type of blood cancer that originates in lymphatic cells of the bone marrow.

acute myelogenous leukemia: Type of blood cancer that involves accumulation of myeloid cells in the bone marrow and bloodstream.

adenocarcinoma: Cancer that begins in cells that line certain internal organs.

adenoma: Noncancerous tumor.

alpha-fetoprotein: Protein often found in abnormal amounts in the blood of patients with liver cancer.

Ames test: Mutagenesis assay (a measure of mutagenic ability) that involves specially engineered strains of bacteria. Because of the relationship between mutagenicity and carcinogenicity, the test is used as a rapid and relatively inexpensive first screening of untested chemicals that are suspected to be carcinogens.

anaplastic: Term used to describe cancer cells that divide rapidly and bear little or no resemblance to normal cells.

angiogenesis: Blood vessel formation, which usually accompanies the growth of malignant tissue.

angiosarcoma: Type of cancer that begins in the lining of blood vessels.

apoptosis: Normal cellular process involving a genetically programmed series of events leading to the death of a cell.

asymptomatic: Presenting no signs or symptoms of disease.

ataxia telangiectasia: Hereditary disorder characterized by problems with muscle coordination, immunodeficiency, inadequate DNA repair, and an increased risk of developing cancer.

atypical hyperplasia: Benign (noncancerous) condition in which tissue has certain abnormal features.

basal cell: Small, round cell found in the lower part, or base, of the epidermis, the outer layer of the skin.

basal cell carcinoma: Type of skin cancer that arises from the basal cells.

benign: Not cancerous; does not invade nearby tissue or spread to other parts of the body.

benign tumor: A noncancerous growth that does not spread to other parts of the body.

biological therapy: Use of the body's immune system, either directly or indirectly, to fight cancer or to lessen side effects that may be caused by some cancer treatments. Also known as immunotherapy, biotherapy, or biological response modifier therapy.

biopsy: Removal of a sample of tissue, which is then examined under a microscope to check for cancer cells.

bone marrow: Soft, spongy tissue in the center of large bones that produces white blood cells, red blood cells, and platelets.

bone marrow aspiration: Removal of a small sample of bone marrow (usually from the hip) through a needle for examination under a microscope to see whether cancer cells are present.

bone marrow biopsy: Removal of a sample of tissue from the bone marrow with a large needle. The cells are checked to see whether they are cancerous. If cancerous plasma cells are found, the pathologist estimates how much of the bone marrow is affected. Bone marrow biopsy is usually done at the same time as bone marrow aspiration.