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A case of pure monocytic, 'Schilling-Type' leukaemia in a 9-year-old boy is described. The leukaemic cells resembled monocytes and were abundantly present in blood and bone marrow. They were strongly alpha-naphthyl-acetate-esterase positive, contained fine PAS-positive granules and did not stain by Sudan B. They were negative for surface bound and intracytoplasmic IgG, but had a high density of membrane Fc-receptors and showed phagocytosis. The surface glycoprotein pattern resembled that of monocytes, but was clearly different from those of lymphocytic and myelocytic cells or those of acute lymphocytic leukaemia cells. The karyotype of bone marrow cells was 44,X, -15, -21, +mar,del(2)(p11), with the missing Y-chromosome located in the marker chromosome. Especially the surface glycoprotein and membrane receptor analyses aided in the accurate classification of the monocytic origin of the leukaemic cells.
Weber et al. (Mon,) studied this question.