nadir The lowest point. Sometimes used to describe the lowest point reached by the blood count after it has been affected by chemotherapy .

nasogastric tube A fine plastic tube that passes in through the nose, down the throat and directly into the stomach. It is used to feed someone who has temporary problems with eating or swallowing.

nebuliser [neb-u-li-ser] A device that turns liquid into a fine mist or spray often used to administer drugs that relieve breathing difficulties.

neck dissection see radical neck dissection .

nephrectomy [neph-rec-to-my] Surgical removal of a kidney. When cancer is the cause of removal, the adrenal gland is also removed.

neoplasm [ne-o-plasm] see tumour .

nerve block A method of numbing a part of the body by injecting a local anaesthetic to block the nerve impulses, including pain, coming from that area.

nervous system The vast network of specialised nerve cells that carry information in the form of nerve impulses to and from all parts of the body in order to bring about bodily activity. It includes the central nervous system (brain and spinal cord), which coordinates activity, and the peripheral nervous system, which comprises all the nerves that lie outside the brain and spinal cord.

neuroblastoma [neu-ro bla-sto-ma] A malignant tumour or cancer that occurs in children which starts in nervous system tissue.

neurofibroma [neu-ro fi-bro-ma] see neuroma .

neurofibromatosis [neu-ro fi-bro-ma to-sis] A congenital condition where there are many benign tumours growing from the fibrous coverings of nerves. They sometimes become malignant . This condition is often associated with a tumour of the adrenal gland.

neuroma [neu-ro-ma] A slow-growing benign tumour (not a cancer ) growing from a nerve. The most common type is an acoustic neuroma, which appears on the acoustic nerve that goes to the ear. They may cause deafness if not treated. Also called neurofibroma, neurilemmoma, neurinoma, Schwannoma.

neurosurgeon [neu-ro sur-geon] A surgeon who specialises in operations on the nervous system , particularly the brain and spinal cord.

node, nodule Both words describe a swelling or lump that may be normal or abnormal: see lymph node .

non-Hodgkin's lymphoma see lymphoma .