Initial core biopsy touch imprints. (a) Wright-Giemsa stained blood-dilute touch imprints; note the packed marrow on the left side. (b) Hemorrhagic necrosis on right side of this H&E stained section. (c) Immunoperoxidase staining of core biopsy for CD33; areas not taking the stain represent necrotic marrow. (d) Immunoperoxidase staining for Myeloperoxidase of a section from core biopsy.