Atypical Blast Crisis in Chronic Myelogenous Leukemia

THE TERMINAL event of chronic myelogenous leukemia (CML) being transformed into a phase indistinguishable from acute leukemia is well recognized. In most instances, there is one preponderant morphological cell type, which usually closely resembles that of acute myelogenous leukemia.1Recent studies indicate that a diverse morphological picture may be present in the peripheral blood and bone marrow of patients with clinically and often cytogenetically documented CML in blast crisis; the preponderant cells may be erythroblastic (rubriblastic), megakaryoblastic, lymphoblastic, promyelocytic, or undifferentiated.2-4This report describes a patient with a diagnosis of CML lasting ten years and terminating with a distinctly heterogeneous blastic transformation, in which myeloblasts, erythroblasts, megakaryoblasts, and undifferentiated blast cells were seen in the peripheral blood and bone marrow. These findings, which were obtained by light and electron microscopic techniques, further support the concept that all hematopoietic elements originate from a common pluripotential stem cell. Report of