The bone marrow shown here is M2 by the FAB classification. More than 3% of the cells are promyelocytes. The cells have more abundant cytoplasm than is seen with Iymphoblasts, and the nuclei are more regular than usually is seen in monoblasts. The patient had more than 40% blasts and promyelocytes in his bone marrow, and, therefore, the case could not be classified as CML. However, it may be difficult to exclude the blast crisis of CML. A careful history should be taken and a thorough physical examination made. If the history of illness is very short, the patient is more likely to have AML. If splenomegaly is present, blast crisis is suspected, since most patients with AML do not have enlarged spleens. If the Ph1 chromosome is present, preexisting CML is more likely; however, its absence is not helpful. The LAP may change in CML and become normal in blast crisis, so it too is not helpful. Also, the test may not be possible to perform since there may not be enough mature granulocytes to count.
Course Section: 08. Myelocytic Leukemia: Chronic and Acute
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