X.B.001

Acute monocytic leukemia. Double esterase stain. Marrow film. Leukemic monocytic cells, the dominant cell population, stain with gray-black color. Two admixed immature neutrophils stain with reddish-brown color. Double esterase combines two substrates: naphthol AS-D chloracetate that reacts with primary granules in the neutrophilic series and α-naphthyl butyrate that stains material in the endoplasmic reticulum of cells in the monocytic lineage.