By Diana Rodriguez

Medically reviewed by Lindsey Marcellin, MD, MPH

You will have a lot to learn and many decisions to make if you're diagnosed with breast cancer. Medical terms can get confusing when you're reading or learning about breast cancer information and breast cancer facts. Don't get lost in unfamiliar breast cancer jargon. Use this glossary as your reference guide for breast cancer facts and information. Adenocarcinoma: The most common type of breast cancer, which begins in glandular tissues of the breast. Adjuvant therapy: Additional therapy used in conjunction with another treatment; for example, using hormonal therapy or chemotherapy in addition to surgery to treat breast cancer. Aromatase inhibitors: Newer drugs used to treat breast cancer; they reduce estrogen production and are considered a type of hormone therapy. Aspiration: Procedure that uses a needle to remove fluid from a lump to determine if cancer cells are present. Atypical hyperplasia: Benign breast condition in which there are abnormalities of the breast. Though not cancer, it is a risk factor for breast cancer. Axillary: Located in the armpit. Benign: Noncancerous. A benign tumor means there is no cancer present. Biological therapy (immunotherapy): A type of breast cancer treatment that boosts the body's immune system and increases its ability to fight cancer. Biopsy: Diagnostic procedure that involves removing a small sample of suspicious tissue to determine whether or not it is cancerous. A suspicious breast lump is biopsied to look for cancer cells. BRCA1 and BRCA2: The two genes that, when mutated, are the cause of most inherited forms of breast and ovarian cancers. Carcinoma: Type of cancer originating in the cells that form the lining of a gland or organ. Chemotherapy: Type of cancer treatment that employs drugs to destroy cancer cells. It's often used in conjunction with other forms of breast cancer treatment. Cyst: A lump consisting of a small, fluid-filled sac. Duct(s): Tube(s) located in the breast that allow(s) milk to reach the nipple for breastfeeding. Ductal carcinoma in situ: Breast cancer confined to the milk ducts in the breast. Estrogen: The hormone produced by the ovaries that gives women characteristics of the female sex. Estrogen is thought to encourage breast cancer cell growth. Estrogen receptor test: A diagnostic laboratory test used to determine if a breast cancer is using estrogen to grow and if hormone therapy should be the treatment course. Herceptin (trastuzumab): A targeted therapeutic agent that is used to treat patients who test positive for the HER2neu gene. See also HER2neu. HER2neu: A receptor gene present in increased amounts in association with some breast cancers. If cancer cells removed from the body test positive for HER2neu, the patient is treated with the therapeutic agent Herceptin, which directly targets the HER2neu receptor site on the cancer cells. Hormonal therapy (hormone therapy): Breast cancer treatment that uses hormones to either promote or inhibit the effects of certain hormones on the cancerous tissue. Immunotherapy: See Biological therapy. Inflammatory breast cancer: A rare (1-5% of cases in U.S.) but very aggressive type of breast cancer in which the cancer cells block the lymph vessels in the skin of the breast. Its symptoms are breast swelling and redness ("inflammation") and a feeling of warmth in the breast. Localized cancer: Cancer confined to one area (in this case, the breast) that hasn't spread elsewhere in the body. Lumpectomy: Breast cancer surgery to remove the breast cancer lump and some surrounding tissue rather than the entire breast. Lymph nodes: Small solid organs (sometimes erroneously referred to as “glands”) in the body that help to protect against foreign substances like bacteria. Breast cancer that has affected the lymph nodes may mean that the cancer has spread elsewhere in the body beyond the breast. Magnetic resonance imaging (MRI): Diagnostic imaging test that provides three-dimensional views of the breast and any abnormalities. Malignant: Cancerous, as in a malignant tumor. Mammography: Diagnostic screening technique using x-ray images to detect breast cancer or other abnormalities. Mastectomy: The surgical removal of a breast. In a double mastectomy, both breasts are removed. Metastasize: The spread of cancer beyond its initial site. If breast cancer has metastasized, it has spread beyond the breasts to other parts of the body. Microcalcifications: Calcium deposits that are too small to be felt but can be spotted on a mammogram. Their presence may indicate breast cancer. Needle biopsy, needle aspiration biopsy: Diagnostic test using a needle to draw a tissue sample, performed under the guidance of mammography or ultrasound. The sample is then be tested for cancer. Oncologist: Medical professional who specializes in cancer (oncology). There are many different oncology specialists, including radiation oncologists, surgical oncologists and medical oncologists, each focused on that particular area of cancer treatment. Raloxifene: Hormonal therapy drug that is very effective in reducing breast cancer risk. Radiation therapy: Type of cancer treatment that uses high doses of radiation (x-rays). Remission: Term used when no signs of cancer are apparent after treatment. Stage: Breast cancer is staged from 0 to IV, according to how large a tumor is and how advanced the cancer is — if and how far it has spread throughout the body. The lower the stage, the less advanced the breast cancer. Systemic therapy: Breast cancer treatment that affects the entire body, such as chemotherapy. Tamoxifen: Hormonal treatment in pill form used to treat breast cancer that is sensitive to estrogen. It is also used as a preventive therapy in women who have many risk factors for developing breast cancer. TNM system: Classification of breast cancer based on three assessments — T for tumor size, N for lymph node involvement, and M for presence or absence of metastatic spread. The TMN classification aids in staging the cancer for making treatment decisions. Triple-negative breast cancer: A type of breast cancer that is shown not to have estrogen, progesterone or HER2neu receptors in testing of cancer cells removed from the body. Therefore, the cancer is not responsive to treatment with hormonal therapy or Herceptin. Tumor: An abnormal mass, which can be either benign or malignant. Ultrasonography: Diagnostic test for breast cancer that uses very high-frequency sound waves to help spot a tumor or breast abnormality. The sound waves are converted into a video or photo, which can indicate the presence of a tumor. Xeloda: Brand name of the oral chemotherapy drug capecitabine, a hormonal therapy treatment for advanced breast cancer. * Modified from Everyday Health, Inc.,