Morphology and immunophenotype of AML1-ETO/+ hematopoietic cells. (A, left-to-right) Typical dysplastic multilineage AML1-ETO/+ colony from passage 16 with prominent hemaglobinization. Wright-Giemsa–stained cytocentrifuge preparation of this colony showing erythroid, monocytic, and megakaryocytic elements. Prominent alpha naphthyl butyrate cytochemical activity in a cluster of myeloid and monocytic cells from within this colony. (B) Flow cytometeric analysis of surface antigen expression in AML1-ETO/+ hematopoietic cells expanded in liquid cultures. Solid black line represents staining obtained with antibodies specific for the indicated hematopoietic antigen. Dashed line corresponds to the signal obtained with an isotype matched control antibody.