Electrical Impedance Imaging (EIS or T-Scan): A diagnostic test that measures how electricity travels though tissue.  Electrical impedance imaging has been approved for use in conjunction with mammography to investigate breast abnormalities.  Also called Transscan or T-scan. 

Ellence: Generic name, epirubicin. Drug used to treat early stage breast cancer after breast surgery in patients whose cancer has spread to the axillary lymph nodes.

Endocrine glands: Glands that release hormones into the bloodstream. The ovaries are one type of endocrine gland.

Endocrine therapy: Manipulation of hormones for therapeutic purposes. (See also hormone therapy).

Engorgement (breast): Breast swelling that can occur when the breasts produce more milk than the amount that is being expelled by breast-feeding, pumping, or manual (hand) expression.  A common problem for breast-feeding mothers, especially during the first two to five days after childbirth.

Epidemiology: The study of factors that have an impact on health and diseases by collecting and analyzing statistical data. In the field of cancer, epidemiologists are studying how many people have cancer; who gets specific types of cancer; and what factors (such as environment, job hazards, family patterns, and personal habits, such as smoking and diet) play a part in the development of cancer.

Epirubicin: Brand name, Ellence. Drug used to treat early stage breast cancer after breast surgery in patients whose cancer has spread to the axillary lymph nodes. 

Estrogen: A female sex hormone produced primarily by the ovaries, and in smaller amounts, by the adrenal cortex. In women, levels of estrogen fluctuate on nature's carefully orchestrated schedule, regulating the development of secondary sex characteristics, including breasts; regulating the monthly cycle of menstruation; and preparing the body for fertilization and reproduction. In breast cancer, estrogen may promote the growth of cancer cells. (See estrogen receptor assay, estrogen replacement therapy).

Estrogen receptor assay: Growth of normal breast cells and some breast cancers are stimulated by estrogen. Estrogen receptors are molecules that function as cells' "welcome mat" for estrogen circulating in the blood. Breast cancer cells without these receptors (called estrogen receptor negative or ER-negative) and may be less likely to respond to hormonal therapy. ER-positive cancers are more likely to respond to hormonal therapy. The estrogen receptor assay is a laboratory test done on a piece of the cancer in order to see whether estrogen receptors are present. (See also progesterone receptor assay).

Estrogen replacement therapy (ERT): The use of exogenous estrogen (estrogen not produced by the body; estrogen from other sources) after the body has ceased to produce it because of natural or induced menopause. This type of hormone therapy is often prescribed to alleviate symptoms of menopause and has been shown to provide protective effects against heart disease and osteoporosis in post-menopausal women. Since estrogen nourishes some types of breast cancer, scientists are working on the question of whether estrogen replacement therapy increases breast cancer risk. There appears to be an emerging consensus that estrogen replacement therapy does not significantly increase the risk for breast cancer. This appears to be true for women who are on estrogen less than five years or who take less than 0.625 mg per day. (See also estrogen, menopause, osteoporosis).  Some new drugs called selective estrogen receptor modulators (SERMs) are being studied. They seem to have many of the beneficial effects of estrogen replacement without increasing breast cancer risk. Recent studies suggest that some SERMs may actually reduce breast cancer risk. (See also estrogen, menopause, osteoporosis).

Etiology: The cause of a disease. In cancer, there are probably many etiologies, although research is showing that both genetics and lifestyle are major factors in many cancers.

Evista: Generic name, raloxifene. Drug used to prevent and treat osteoporosis.  Evista is also being studied to determine whether it can safely and effectively prevent breast cancer in women at high risk for the disease since it is chemically similar to the drug tamoxifen.

Excisional biopsy: The removal of the entire suspected breast lump and a surrounding margin of normal tissue.

Exemestane: Brand name, Aromasin. Drug used to treat metastatic breast cancer in post-menopausal women.   Works by binding to the body's aromastase enzyme, an enzyme responsible for producing the hormone, estrogen. 

Extended radical mastectomy:See mastectomy.