tamoxifen A hormonal treatment that blocks the action of oestrogen in the breast.

TENS see transcutaneous electric nerve stimulation.

teratoma [ter-a-to-ma] A tumour made up of a number of different types of tissue, none of which is normally found in the area where the tumour occurs. A teratoma may be benign (not a cancer) or malignant (a cancer). Benign teratomas may become malignant. They occur most often in the testis and ovary ; they may occur in children though most frequently in adults: see testicular cancer.

terminal An illness is described as terminal when the person is expected to die of that illness within months or weeks. Patients receiving hospice care are usually in the terminal phase of an illness

testicular cancer [tes-tic-u-lar can-cer] Cancer of the testis: a rare disease that occurs most often in men aged between 20 and 35. The most common cancers of the testis are seminomas (70 per cent) and teratomas (25-30 percent). Many testicular cancers can now be cured.

testosterone [tes-tos-ter-one] The main male sex hormone. It is produced by the testes, and stimulates male sexual activity and the growth of other sex organs including the prostate.

thoracic spine [thor-ac-ic] The part of the backbone (spine) to which the ribs are attached; the part behind the chest.

thrombocytopenia [throm-bo cy-to pe-ni-a] A decrease in the number of platelets in the blood which causes blood to take longer than usual to clot when there is bleeding. In cancer, thrombocytopenia may occur when cancer cells replace normal cells in the bone marrow, or as a result of chemotherapy.

thrombosis [throm-bo-sis] The formation or presence of a blood clot. When this occurs inside a blood vessel, it can block the flow of blood. In the brain, a blockage causes a stroke; in the heart, it can cause a heart attack; elsewhere in the body, it can damage nearby tissues.

thymus [thy-mus] An organ below the neck, above and in front of the heart. In infants, it controls development of lymphoid tissue and the immune response. In adults its function is uncertain.

thyroid gland [thy-roid] A large gland in the neck, with two lobes that wrap around either side of the windpipe (trachea ) just below the voice box (larynx ). It secretes thyroid hormone, which regulates the rate at which the body uses food and oxygen, and the rate at which various organs function.

tissue Refers to a collection of cells which are specialised for a particular body function.

tissue expander A device that may be used in breast reconstruction after mastectomy if a woman does not have quite enough skin left to cover a breast implant .

tissue typing Tissue typing is done when a bone marrow or organ transplant is being planned. It involves looking at the tissues of both the potential donor and the person receiving the transplant to measure how compatible they are.

titration [ti-tra-tion] In chemotherapy, this means finding the right dose of a chemotherapy drug that will destroy cancer cells most effectively while keeping the effects on normal tissue to a safe, tolerable level.

tolerance If a person takes a particular drug (or medicine) over some time, the drug may gradually become less effective as their body may respond less to it. This is known as drug tolerance. If this happens, it may be necessary either to increase the dose or change to another drug.

tomography [to-mog-ra-phy] The technique of building up cross-sectional pictures (pictures showing a slice through) of an organ or part of the body, using x-rays : see CT scan

total body irradiation Radiotherapy to the entire body so that, theoretically, all cells in the body receive the same amount (or dose) of radiation.

trans cutaneous electric nerve stimulation (TENS) A technique used to relieve pain using a weak electric current, the impulses of which produce a mild tingling sensation.

transfusion Where blood or blood products (plasma, particular blood cells) taken from a healthy person are given to someone whose blood is in some way deficient. The blood drips slowly through a needle directly into one of the recipient's veins. A cancer patient may receive a transfusion of red blood cells that carry oxygen, granulocytes (a type of white blood cell ) that fight infection, or platelets that help the blood to clot. Blood transfusions are also routinely given during many major operations

transitional cells Cells lining some organs.

transurethral resection (TUR) [trans-u-reth-ral re-sec-tion] Removal, via the penis, of a tumour in the bladder or the prostate . No cut to the skin is needed as an instrument is inserted through the urethra. TUR can be used only for very small

tumours: see resection.

tumour A new or abnormal growth of tissue in or on the body. A tumour may be benign (not a cancer) or malignant (a cancer). The term 'neoplasm ' usually describes malignant tumours .

tumour marker A substance which, if found in the body, suggests that there may be a tumour present.

TUR see transurethral resection.