The leukaemogenic effect of whole-body irradiation of the mouse: Experimental work at the Radiobiological Research Unit, Harwell

Mouse 'leukaemia' is a generic term which might well be replaced by the clumsier, but more accurate, 'malignant disease of reticular tissue'. There are a variety of cytologically definable types (reticulosarcoma, 'histiocytoma' or monocytic leukaemia, lymphosarcoma and lymphoid leukaemia, myeloid leukosis) and a variety of morbid anatomical patterns, but there is only an approximate correlation between morbid anatomy and cytological type. True leukaemia where the white blood cell count is raised and morphologically abnormal white cells are found in the blood) occurs but is relatively uncommon; leukaemoid blood pictures are also found. Normally the murine thymus persists for much of the reproductive life-span, atrophying only in middle age, instead of in early childhood as in man. This may be the reason why the anatomical region of the thymus is more often involved in leukaemia in younger than in older animals, and why 'thymic leukaemia' is a characteristically murine disease and does not seem to occur in man. A great deal of the experimental work on mouse leukaemia reported in the literature is concerned with 'thymic leukaemia,' and this is often considered to be synonymous with thymic lymphoma or lymphosarcoma. However, the anatomy of tumour masses in the superior mediastinum. not infrequently suggests that they are not truly thymic in origin and their cell type is often not lymphoid