Alkaline phosphatase-positive leukemic monocytes in a child with acute monocytic leukemia

A subpopulation with alkaline phosphatase activity and neutrophilic granules was found in leukemic monocytes from a child with acute monocytic leukemia (M5B). Almost all leukemic cells were strongly positive for nonspecific esterase and phagocytized opsonized zymosans. These findings suggest that the subpopulation are chimeric cells with characteristics of both monocytic and neutrophilic cell lines. The leukemogenesis in this patient might involve the simultaneous expression of differentiation genes otherwise restricted to either cell lineage.