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.

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.

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 Institute 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.

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 aspiration.

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

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

Neoadjuvant therat therapy: Treatment given before the primary treatment. Neo-adjuvant 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.

Neuro: 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. 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 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.