Necrosis: Term used to describe the death of cellular tissue. Necrosis within a cancerous tumor may indicate that the tumor is growing so rapidly that blood vessels are not able to multiply fast enough to nourish some of the cancer cells. Necrosis usually indicates that the tumor is very aggressive and can spread quickly. Fat necrosis is a benign (non-cancerous) breast condition that may occur when fatty breast tissue swells or becomes tender spontaneously or as the result of an injury to the breast.

Needle aspiration: A type of needle biopsy. Removal of fluid from a cyst or cells from a tumor. In this procedure, a needle and syringe (like those used to give injections) is used to pierce the skin, reach the cyst or tumor, and with suction, draw up (aspirate) specimens for biopsy analysis. If the needle is thin, the procedure is called a fine needle aspiration or FNA. (See also needle biopsy).

Needle biopsy: Removal of fluid, cells, or tissue with a needle for examination under a microscope. There are two types: fine needle aspiration (also called FNA or needle aspiration) and core biopsy. FNA uses a thin needle and syringe (like those used to give injections) to pierce the skin and draw up (aspirate) fluid or small tissue fragments from a tumor. A core needle biopsy uses a thicker needle to remove a cylindrical sample of tissue from a tumor.

Needle localization: Also called wire localization. A procedure used to guide a surgical breast biopsy when the breast lump is difficult to locate or in areas that look suspicious on the x-ray (mammogram) but do not have a distinct lump. Mammogram or ultrasound images are used to guide the needle to the suspicious area of the breast. The radiologist typically replaces the needle with a wire and sends the patient to the surgeon with only a wire in place.  The surgeon then uses the path of the wire as a guide to locate the abnormal area to be removed. Needle localization is usually used when there is no palpable (able to be felt) lump (i.e., a finding found only or most convincingly on an imaging study such as a mammogram or ultrasound.

Neoadjuvant therapy: Treatment such as chemotherapy or hormonal therapy that is given to a patient prior to surgery.  Neoadjuvant therapy may help shrink breast tumors so that they may be removed with a less complicated surgical procedure.

Neoplasm: An abnormal growth (tumor) that starts from a single altered cell, a neoplasm may be benign (non-cancerous) or malignant (cancerous). Cancer is a malignant neoplasm.

Neupogen: Generic name, filgrastim. A drug used to treat neutropenic patients (those with a decreased white blood cell count).

Neutropenia: An abnormal decrease in white blood cells most often resulting from a viral infection or exposure to certain drugs or chemicals.  Neutropenia may be a side effect of chemotherapy.

Nipple: The tip of the breast; the pigmented projection in the middle of the areola. The nipple contains the opening of milk ducts from the breast. The nipple consists mainly of skin and ductal breast tissue. 

Nipple confusion: A fairly common condition in which the baby becomes “confused” between the mother’s nipple and an artificial nipple of a bottle. Babies with nipple confusion will not latch on to the mother’s nipple and become fussy when a mother tries to breast-feed.

Nipple discharge: Any fluid coming from the nipple. It may be clear, milky, bloody, tan, gray, or green.

Nodal status: Indicates whether a breast cancer has spread (node-positive) or has not spread (node-negative) to lymph nodes in the armpit (axillary nodes). The number and site of positive axillary nodes can help predict the risk of cancer recurrence.   

Node: See lymph node.

Nodule: A small, solid lump that can be located by touch. Also called mass or nodule.  

Nolvadex: Trade name for tamoxifen; an antiestrogen drug commonly used in breast cancer therapy. (See also antiestrogen, tamoxifen, hormonal therapy).

Noncancerous: Benign; no cancer is present; not malignant.

Noninvasive breast cancer: Cancer cells that are confined to the breast ducts and do not invade surrounding fatty and connective tissues of the breast. Ductal carcinoma in situ (DCIS) is the most common form of noninvasive breast cancer (90%). Lobular carcinoma in situ (LCIS) is less common and considered a marker for increased breast cancer risk.

Nonpalpable: A breast abnormality that is present but unable to detect by touch.  Mammography helps detect many nonpalpable breast cancers in an early stage.

Normal hormonal changes: Changes in breast and other tissues that are caused by fluctuations in levels of female hormones during the menstrual cycle.

Nuclear magnetic resonance (NMR): See magnetic resonance imaging.

Nuclear medicine scan: A method for localizing diseases of internal organs such as the brain, liver, or bone, in which small amounts of a radioactive substance (isotope) are injected into the bloodstream. The isotope is concentrated in certain organs. A scintillation (nuclear medicine) camera is used to produce an image of the organ and detect areas of disease.

Nucleus: The center of a cell where the DNA is housed and replicated. Studying the size and shape of a cell’s nucleus under the microscope can help pathologists distinguish breast cancer cells from benign (non-cancerous) breast cells.

Nulliparous: A woman who has never given birth to a child.

Nurse practitioner: A registered nurse (RN) who has completed additional courses and specialized training. Nurse practitioners can work with or without the supervision of a physician. They take on additional duties in diagnosis and treatment of patients, and in many states they may write prescriptions. (See also oncology nurse specialist).