A case of aCML. (Left) BM biopsy (hematoxylin and eosin, ×500) reveals a hypercellularity (100%) with markedly increased myeloid:erythroid ratio (26:1). Dysplastic megakaryocytes are indicated by arrows; (right) PB smear (Wright Giemsa, ×1000) shows marked leukocytosis with many myeloid precursors (promyelocytes, myelocytes, and metamyelocytes, 23%). Neutrophils show peculiar abnormal nuclear segmentation. (Microscope: Olympus, Tokyo, Japan; camera and software: Q-Capture, Surrey, Canada.)