Eosinophilic leukemia with prominent visceral involvement: histopathological and histochemical observations

Evidence supporting the view that eosinophilic leukemia exists as a separate entity among myeloproliferative disorders was found in the pathological and histochemical findings in a case of hypereosinophilic disease. Blast cells and eosinophils in all stages of maturity, including unusual atypical eosinophil precursors, were seen in a prominent infiltration of the spleen and the liver. Blasts were far more numerous in the viscera, especially in the liver, than in the marrow and peripheral blood. Enzyme histochemical studies of plastic sections showed that blasts were reactive for cyanide-resistant peroxidase, which is specific for eosinophils, and could therefore be regarded as part of an eosinophilic leukemic proliferation. Some eosinophils showed aberrant reactivity for chloroacetate esterase. The existence of a neoplastic proliferation of eosinophils is consistent with the view that eosinophils represent a distinct marrow line. The possibility that hypereosinophilic patients may harbor a far more prominent blastosis in the viscera than is apparent from marrow and blood picture is also stressed. Finally, a chromosomic abnormality previously described in acute nonlymphocytic leukemia with atypical eosinophils in the marrow is for the first time reported in a patient with hypereosinophilic disease.