Normal marrow cells. Peroxidase stain. (A) Large promyelocyte stains intensely (blue-black color) because of the abundant primary granules in cytoplasm (asterisk). Myelocytes and segmented neutrophil also stain but less intensely because of the decreasing concentration of primary granules.
Acute myelogenous leukemia. Peroxidase stain. Marrow films. Left panel: note positive stain for cytoplasmic granules and Auer rod in each of two blast cells. Right panel: peroxidase stain and Wright-Giemsa stain. Note two peroxidase positive blast cells. The upper of two blast cells contains an Auer rod highlighted by the peroxidase stain.
Acute lymphocytic leukemia. Peroxidase stain. Note neutrophil reacts positively with peroxidase stain. The remaining leukemic lymphoblasts are not stained.