Chronic myelogenous leukemia morphology and immunophenotype

Chronic myelogenous leukemia (CML) is a clonal stem cell disorder that is hallmarked by the presence of a t(9;22), also known as the Philadelphia chromosome. Morphologic examination of the peripheral blood and marrow is helpful to characterize the patient's disease phase, including chronic, accelerated, and blast. The chronic phase is hallmarked by a peripheral blood with leukocytosis, basophilia, and a myelocyte bulge. The accelerated and blast phases are typically characterized by increased blasts, myeloid and/or lymphoid. Flow cytometry has an additional diagnostic role and is helpful to document atypical blast and/or maturing myeloid cells in the blood and marrow. It is most helpful to document lineage and aberrant immunophenotype in a blast crisis. This chapter will summarize the morphologic and immunophenotypic criteria used when evaluating patients with CML.