Myeloblasts with Auer rods

These four images were taken from the March 2001 Cytohematology Proficiency Test Event - Slide 036. The myeloblast is the first stage of the granulocytic series that is identifiable by light microscopy. It may be difficult to distinguish myeloblasts from other blasts in the peripheral blood unless one uses special stains or infers their identity from the presence of other immature cells of the same line. A myeloblast can be distinguished from a promyelocyte by its lack of cytoplasmic granulation. The nucleus is composed of very fine nonaggregated chromatin that stains light blue to reddish-purple with Wright's stain. Two to five distinct nucleoli are usually present. The nucleus is often bordered at one side by a distinct perinuclear zone. Auer rods are elongated, bluish-red rods composed of fused lysosomal granules, seen in the cytoplasm of myeloblasts, promyelocytes and monoblasts and in patients with acute myelogenous leukemia. Back to Slide 036