Abscess: A pocket of pus that forms as the body's defenses attempt to wall off infection-causing germs.

Areola: The colored tissue that encircles the nipple.

Aspiration: Removal of fluid from a cyst or cells from a lump, using a needle and syringe.

Benign: Not cancerous; cannot invade neighboring tissues or spread to other parts of the body.

Biopsy: The removal of a sample of tissue or cells for examination under a microscope for purposes of diagnosis.

Breast density: Glandular tissue in the breast common in younger women, making it difficult for mammography to detect breast cancer.

Breast implants: Silicone rubber sacs, which are filled with silicone gel or sterile saline, used for breast reconstruction after mastectomy.

Calcifications: Small deposits of calcium in tissue, which can be seen on mammograms.

Cancer: A general name for more than 100 diseases in which abnormal cells grow out of control. Cancer cells can invade and destroy healthy tissues, and they can spread through the bloodstream and the lymphatic system to other parts of the body.

Carcinoma: Cancer that begins in tissues lining or covering the surfaces (epithelial tissues) of organs, glands, or other body structures. Most cancers are carcinomas.

Carcinoma in situ: Cancer that is confined to the cells where it began, and has not spread into surrounding tissues.

Chemoprevention: The use of drugs or vitamins to prevent cancer in people who have precancerous conditions or a high risk of cancer, or to prevent the recurrence of cancer in people who have already been treated for it.

Clinical breast exam: A physical examination by a doctor or nurse of the breast, underarm, and collarbone area, first on one side, then on the other.

Cyclic breast changes: Normal tissue changes that occur in response to the changing levels of female hormones during the menstrual cycle. Cyclic breast changes can produce swelling, tenderness, and pain.

Cyst: Fluid-filled sac. Breast cysts are benign.

Ducts: Channels that carry body fluids. Breast ducts transport milk from the breast's lobules out to the nipple.

Ductal carcinoma in situ (DCIS): Cancer that is confined to the ducts of the breast tissue.

False negative (mammograms): Breast x-rays that miss cancer when it is present.

False positive (mammograms): Breast x-rays that indicate breast cancer is present when the disease is truly absent.

Fat necrosis: Lumps of fatty material that form in response to a bruise or blow to the breast.

Fibrocystic disease: See Generalized breast lumpiness.

Fine needle aspiration: The use of a slender needle to remove fluid from a cyst or clusters of cells from a solid lump.

Frozen section: A sliver of frozen biopsy tissue. A frozen section provides a quick preliminary diagnosis but is not 100 percent reliable.

Generalized breast lumpiness: Breast irregularities and lumpiness, commonplace and noncancerous. Sometimes called "fibrocystic disease" or "benign breast disease."

Genetic change: An alteration in a segment of DNA, which can disturb a gene's behavior and sometimes leads to disease.

Higher risk (for breast cancer): A measure of the chances of getting breast cancer when factor(s) known to be associated with the disease are present.

Hormone replacement therapy: Hormone-containing medications taken to offset the symptoms and other effects of the hormone loss that accompanies menopause.

Hormones: Chemicals produced by various glands in the body, which produce specific effects on specific target organs and tissues.

Hyperplasia: Excessive growth of cells. Several types of benign breast conditions involve hyperplasia.

Infection: Invasion of body tissues by microorganisms such as bacteria and viruses.

Infiltrating cancer: Cancer that has spread to nearby tissue, lymph nodes under the arm, or other parts of the body. (Same as invasive cancer.)

Inflammation: The body's protective response to injury (including infection). Inflammation is marked by heat, redness, swelling, pain, and loss of function.

Intraductal papilloma: A small wartlike growth that projects into a breast duct.

Invasive cancer: Cancer that has spread to nearby tissue, lymph nodes under the arm, or other parts of the body. (Same as infiltrating cancer.)

Laser beam scanning: a technology being studied in research for breast cancer detection that shines a laser beam through the breast and records the image produced, using a special camera.

Lobes, lobules, bulbs: Milk-producing tissues of the breast. Each of the breast's 15 to 20 lobes branches into smaller lobules, and each lobule ends in scores of tiny bulbs. Milk originates in the bulbs and is carried by ducts to the nipple.

Localization biopsy: The use of mammography to locate tissue containing an abnormality that can be detected only on mammograms, so it can be removed for microscopic examination.

Lumpectomy: Surgery to remove only the cancerous breast lump; usually followed by radiation therapy.

Lymphatic system: The tissues and organs that produce, store, and transport cells that fight infection and disease.

Magnetic resonance imaging (MRI): A technique that uses a powerful magnet linked to a computer to create detailed pictures of areas inside the body.

Malignancy: State of being cancerous. Malignant tumors can invade surrounding tissues and spread to other parts of the body.

Mammary duct ectasia: A benign breast condition in which ducts beneath the nipple become dilated and sometimes inflamed, and which can cause pain and nipple discharge.

Mammogram: An x-ray of the breast.

Mammography: The examination of breast tissue using x-rays.

Mastectomy: Surgery to remove the breast (or as much of the breast as possible).

Mastitis: Infection of the breast. Mastitis is most often seen in nursing mothers.

Menopause: The time when a woman's monthly menstrual periods cease. Menopause is sometimes called the "change of life."

Menstrual cycle: The monthly cycle of discharge, during a woman's reproductive years, of blood and tissues from the uterus.

Mutation: A change in the number, arrangement, or molecular sequence of a gene.

Nipple discharge: Fluid coming from the nipple.

Nonpalpable cancer: Cancer in breast tissue that can be seen on mammograms but that cannot be felt.

One-step procedure: Biopsy and surgical treatment combined into a single operation.

Palpation: Use of the fingers to press body surfaces, so as to feel tissues and organs underneath. Palpating the breast for lumps is a crucial part of a physical breast examination.

Permanent section: Biopsy tissue specially prepared and mounted on slides so that it can be examined under a microscope by a pathologist.

Phytochemicals: Naturally occurring chemicals found in plants that may be important nutrients for reducing a person's cancer risk.

Rad: A unit of measure for radiation. It stands for radiation absorbed dose.

Radiation: Energy carried by waves or by streams of particles. Various forms of radiation can be used in low doses to diagnose disease and in high doses to treat disease. 

Risk: A measure of the likelihood of some uncertain or random event with negative consequences for human life or health.

Risk factors (for cancer): Conditions or agents that increase a person's chances of getting cancer. Risk factors do not necessarily cause cancer; rather, they are indicators, statistically associated with an increase in likelihood.

Sclerosing adenosis: A benign breast disease that involves the excessive growth of tissues in the breast's lobules.

Sonogram: The image produced by ultrasound.

Tamoxifen: A hormonally related drug that has been used to treat breast cancer and is being tested as a possible preventive strategy.

Tumor: An abnormal growth of tissue. Tumors may be either benign or cancerous.

Tumor markers: Proteins (either amounts or unique variants) made by altered genes in cancer cells that are involved in the progression of the disease.

Two-step procedure: Biopsy and treatment done in two stages, usually a week or two apart.

Ultrasound: The use of sound waves to produce images of body tissues.