| acute lymphoblastic leukaemia | <haematology> A rapidly progressing cancer of the blood affecting the type of white blood cell known as lymphocytes. Approximately 650 new cases are diagnosed every year in the UK and it is the most common form of childhood leukaemia. Acronym: ALL Origin: Gr. Haima = blood (11 Nov 1997) |
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| common acute lymphoblastic leukaemia | <haematology, oncology> A sub-type of acute lymphoblastic leukaemia affecting cells early in the B lymphocyte lineage which accounts for about 80% of all acute lymphoblastic leukaemia. Origin: Gr. Haima = blood (13 Nov 1997) |
| leukemia | <haematology> An acute or chronic disease of unknown cause in man and other warm blooded animals that involves the blood forming organs, is characterised by an abnormal increase in the number of leucocytes in the tissues of the body with or without a corresponding increase of those in the circulating blood and is classified according of the type leucocyte most prominently involved. (18 Nov 1997) |
| null cell | Lymphocytes lacking typical markers of T or B-cells capable of lysing a variety of tumour or virus infected cells without obvious antigenic stimulation, also effect antibody dependent cell cytotoxicity, carry in humans CD16 marker. (18 Nov 1997) |
| null-cell adenoma | <tumour> An adenoma of the hypophysis composed of cells for which there is no overt evidence or hormone production, but which usually produces hypopituitarism and visual disturbances by compression of adjacent structures; approximately one third of these tumours have cells with abundant mitochondria (oncocytes) that are somewhat larger than the monocytic null cells. Synonym: undifferentiated cell adenoma. (05 Mar 2000) |
| lymphoblastic | Pertaining to the production of lymphocytes. (05 Mar 2000) |
| lymphoblastic leukaemia | Acute lymphocytic leukaemia in which the abnormal cells are chiefly (or almost totally) blast forms of the lymphocytic series, or in which unusually large numbers of the immature forms occur in association with adult lymphocytes. (05 Mar 2000) |
| lymphoblastic lymphoma | <tumour> A diffuse lymphoma in children, with supradiaphragmatic distribution and T lymphocytes having convoluted nuclei; many patients develop acute lymphoblastic leukaemia. (05 Mar 2000) |
| lymphoma, lymphoblastic | A high-grade malignant lymphoma composed of a diffuse, relatively uniform proliferation of cells with round or convoluted nuclei and scanty cytoplasm. The cells are cytologically similar to the lymphoblasts seen in acute lymphocytic leukaemia, and in some cases, the disease may evolve into a leukaemic phase morphologically indistinguishable from acute t-lymphocytic leukaemia (leukaemia, T-cell, acute). Lymphoblastic lymphoma represents approximately one-third of the cases of non-hodgkin's lymphomas in children and 5% of the cases in adults. It is more prevalent in males. (12 Dec 1998) |
| Rh null syndrome | <syndrome> A lack of all Rh antigens, compensated haemolytic anaemia, and stomatocytosis. (05 Mar 2000) |
| null | 1. Something that has no force or meaning. 2. That which has no value; a cipher; zero. <physics> Null method, a zero method. See Zero. Source: Websters Dictionary (01 Mar 1998) |
| null cells | Large granular lymphocytes that lack surface markers/membrane associated proteins of either B or T lymphocytes. (05 Mar 2000) |
| null hypothesis | The assumption that any observed difference between two samples of a statistical population is purely accidental and not due to systematic causes. (05 Dec 1998) |
| null mutation | Change in a gene that leads to nothing, for example to no enzyme or to a nonfunctioning enzyme. (12 Dec 1998) |
| lymphocytes, null | A class of lymphocytes characterised by the lack of surface markers specific for either t or b lymphocytes. (12 Dec 1998) |