Cytochemical "normal" and "abnormal" eosinophils in acute leukemias.

Eosinophilic leukocytes may accompany a great variety of disorders and different types of acute leukemias. The most striking morphologic feature of eosinophils is their specific granules, but morphology alone often is insufficient to differentiate normal from abnormal eosinophils. Cytochemically, the eosinophils were considered "normal" when they did not contain alkaline phosphatase, chloroacetate esterase, toluidine blue metachromasia, Astra blue positivity, and specific PAS-positive granules, but did have peroxidase and cyanide-resistant peroxidase activities, Sudan black positivity and moderate naphthol-AS esterase or alpha-naphthyl esterase and acid phosphatase positivities. In seven cases of acute leukemias (two acute myeloblastic and five myelomonocytic), in contrast with their normal behaviour, the eosinophils show "abnormal" cytochemical positivities consisting of chloroesterase activity, PAS and Astra blue positivities of the specific granules, toluidine blue metachromasia, and cyanide-resistant peroxidase of a few specific granules. Cytochemical investigations may provide additional criteria for evaluating the abnormality of the eosinophilic cell in leukemias.