Acute leukaemia with eosinophilia or acute eosinophilic leukaemia: a dilemma

A young male patient is described with acute leukaemia whose bone marrow and peripheral blood contained abundant cells of the eosinophilic series in all stages of maturation. These cells, proven histochemically to be true eosinophils, were abnormal in both maturation and proliferation. Upon electron microscopic study of bone marrow and peripheral blood, abnormalities in the eosinophilic series were identified as early as the promyelocytic stage as well as in the most mature eosinophil seen. The clinical and morphologic picture of this patient's disease raises the possibility of this being an acute eosinophilic leukaemia.