The bone marrow from the dog with the large numbers of blasts in peripheral blood (see related image) and pancytopenia is essentially effaced by the blasts, some of which had monocytoid nuclei and coarse red-purple granulation (almost resembling mast cell granules). This confirms a diagnosis of acute leukemia (>20% blasts in bone marrow), which was classified as an acute monoblastic leukemia (AML subtype 5a), on cytochemical staining. Along with the blasts, there are low numbers of plasma cells (arrow) and phagocytic macrophages (arrowhead). No other hematopoietic precursors are seen, indicating myelophthisis, which has resulted in the peripheral pancytopenia (Wright’s stain, 500x magnification)
