N-acetyl cysteine: An antioxidant drug that may keep cancer cells from developing or reduce the risk of growth of existing cancer.

nasal: By or having to do with the nose.

nasopharynx (NAY-zo-fair-inks): The upper part of the throat behind the nose. An opening on each side of the nasopharynx leads into the ear.

National Cancer Institute: NCI. The National Cancer Institute, part of the National Institutes of Health of the United States Department of Health and Human Services, is the federal government's principal agency for cancer research. NCI conducts, coordinates, and funds cancer research, training, health information dissemination, and other programs with respect to the cause, diagnosis, prevention, and treatment of cancer. Access the NCI Web site at http://cancer.gov.

National Institutes of Health: NIH. The National Institutes of Health, the focal point of biomedical research in the United States, conducts research in its own laboratories; supports the research of non-federal scientists in universities, medical schools, hospitals, and research institutions throughout the country and abroad; helps in the training of research investigators; and fosters communication of medical information. Access the NIH Web site at http://www.nih.gov.

natural killer cells: NK cells. A type of white blood cell that contains granules with enzymes that can kill tumor cells or microbial cells. Also called large granular lymphocytes (LGL).

NCI: National Cancer Institute. NCI, part of the National Institutes of Health of the United States Department of Health and Human Services, is the federal government's principal agency for cancer research. NCI conducts, coordinates, and funds cancer research, training, health information dissemination, and other programs with respect to the cause, diagnosis, prevention, and treatment of cancer. Access the NCI Web site at http://cancer.gov.

nebulizer: A device used to turn liquid into a fine spray.

neck dissection (dye-SEK-shun): Surgery to remove lymph nodes and other tissues in the neck.

necrosis (ne-KRO-sis): Refers to the death of living tissues.

needle biopsy: The removal of tissue or fluid with a needle for examination under a microscope. Also called fine-needle htmliration.

negative axillary lymph nodes: Lymph nodes in the armpit that are free of cancer.

nelfinavir mesylate: A drug that interferes with the ability of a virus to make copies of itself.

neoadjuvant therapy: Treatment given before the primary treatment. Neoadjuvant therapy can be chemotherapy, radiation therapy, or hormone therapy.

neoplasia (NEE-o-PLAY-zha): Abnormal and uncontrolled cell growth.

neoplasm: A new growth of benign or malignant tissue.

neoplastic meningitis: Tumor cells that have spread from the original (primary) tumor to the tissue that covers the brain, spinal cord, or both.

nephrectomy (nef-REK-toe-mee): Surgery to remove a kidney. Radical nephrectomy removes the kidney, the adrenal gland, nearby lymph nodes, and other surrounding tissue. Simple nephrectomy removes only the kidney. Partial nephrectomy removes the tumor but not the entire kidney.

nephrotomogram (nef-ro-TOE-mo-gram): A series of x-rays of the kidneys. The x-rays are taken from different angles and show the kidneys clearly, without the shadows of the organs around them.

neuroblastoma: Cancer that arises in immature nerve cells and affects mostly infants and children.

neuroectodermal tumor: A tumor of the central or peripheral nervous system.

neuroendocrine (NOO-ro-EN-do-krin): Having to do with the interactions between the nervous system and the endocrine system. Describes certain cells that release hormones into the blood in response to stimulation of the nervous system.

neuroendocrine tumor: A tumor derived from cells that release a hormone in response to a signal from the nervous system. Some examples of neuroendocrine tumors are carcinoid tumors, islet cell tumors, medullary thyroid carcinoma, and pheochromocytoma. These tumors secrete hormones in excess, causing a variety of symptoms.

neurologic: Having to do with nerves or the nervous system.

neurologist (noo-ROL-o-jist): A doctor who specializes in the diagnosis and treatment of disorders of the nervous system.

neuroma (noo-RO-ma): A tumor that arises in nerve cells.

neuropathy: A problem in any part of the nervous system except the brain and spinal cord. Neuropathies can be caused by infection, toxic substances, or disease.

neuropeptide: A member of a class of protein-like molecules made in the brain. Neuropeptides consist of short chains of amino acids, with some functioning as neurotransmitters and some functioning as hormones.

neurosurgeon (NOO-ro-SER-jun): A doctor who specializes in surgery on the brain, spine, and other parts of the nervous system.

neurotoxicity: The tendency of some treatments to cause damage to the nervous system.

neurotoxin: A substance that is poisonous to nerve tissue.

neutropenia: An abnormal decrease in the number of neutrophils, a type of white blood cell.

neutrophil (NOO-tro-fil): A type of white blood cell.

nevus (NEE-vus): A benign growth on the skin, such as a mole. A mole is a cluster of melanocytes and surrounding supportive tissue that usually appears as a tan, brown, or flesh-colored spot on the skin. The plural of nevus is nevi (NEE-vye).

NG-monomethyl-L-arginine: An amino acid derivative used to counteract high blood pressure caused by interleukin-2.

niacinamide: A vitamin being studied to increase the effect of radiation therapy on tumor cells. Also called nicotinamide.

NIH: National Institutes of Health. NIH, the focal point of biomedical research in the United States, conducts research in its own laboratories; supports the research of non-federal scientists in universities, medical schools, hospitals, and research institutions throughout the country and abroad; helps in the training of research investigators; and fosters communication of medical information. 

nilutamide: A drug that blocks the effects of male hormones in the body. It belongs to the family of drugs called antiandrogens.

nimodipine: Belongs to a family of drugs called calcium channel blockers. It is being investigated for use with anticancer drugs to prevent or overcome drug resistance and improve response to chemotherapy.

nipple discharge: Fluid coming from the nipple.

nitric acid: A toxic, corrosive, colorless liquid used to make fertilizers, dyes, explosives, and other chemicals.

nitrocamptothecin: An alkaloid drug belonging to a class of anticancer agents called topoisomerase inhibitors.

nitrosoureas (nye-TRO-so-yoo-REE-ahz): A group of anticancer drugs that can cross the blood-brain barrier. Carmustine and lomustine are nitrosoureas.

node-negative: Cancer that has not spread to the lymph nodes.

node-positive: Cancer that has spread to the lymph nodes.

nolatrexed: An anticancer drug that belongs to the family of drugs called thymidylate synthase inhibitors. Also called AG337.

non-Hodgkin's lymphoma: A group of cancers of the lymphoid system, including acute lymphoblastic leukemia, B-cell lymphoma, Burkitt's lymphoma, diffuse cell lymphoma, follicular lymphoma, immunoblastic large cell lymphoma, lymphoblastic lymphoma, mantle cell lymphoma, mycosis fungoides, post-transplantation lymphoproliferative disorder, small non-cleaved cell lymphoma, and T-cell lymphoma.

non-small cell lung cancer: A group of lung cancers that includes squamous cell carcinoma, adenocarcinoma, and large cell carcinoma.

nonblinded: Describes a clinical trial or other experiment in which the researchers know what treatments are being given to each study subject or experimental group. If human subjects are involved, they know what treatments they are receiving.

nonhematologic cancer: Cancer that does not begin in the blood or bone marrow.

nonmalignant: Not cancerous.

nonmalignant hematologic disorders: Disorders of the blood, some of which lead to leukemia.

nonmelanoma skin cancer: Skin cancer that arises in basal cells or squamous cells but not in melanocytes (pigment-producing cells of the skin).

nonmelanomatous: Skin cancer that arises in basal cells or squamous cells but not in melanocytes (pigment-producing cells of the skin).

nonmetastatic: Cancer that has not spread from the primary (original) site to other sites in the body.

nonrandomized clinical trial: A clinical trial in which the participants are not assigned by chance to different treatment groups. Participants may choose which group they want to be in or they may be assigned to the groups by the researchers.

nonseminoma (non-sem-ih-NO-ma): A group of testicular cancers that begin in the germ cells (cells that give rise to sperm). Nonseminomas are identified by the type of cell in which they begin and include embryonal carcinoma, teratoma, choriocarcinoma, and yolk sac carcinoma.

nonspecific immune cells: Cells such as phagocytes and macrophages that respond to many antigens, not just one antigen.

novobiocin: An antibiotic drug used to treat infection.

NR-LU-10 antigen: A protein found on the surface of some cancers.

NSAIDs: Nonsteroidal anti-inflammatory drugs. A group of drugs that decrease fever, swelling, pain, and redness.

nuclear magnetic resonance imaging: NMRI. A procedure in which a magnet linked to a computer is used to create detailed pictures of areas inside the body. Also called magnetic resonance imaging (MRI).

nystatin: A drug that treats infections caused by fungi.