The first stain we use to differentiate blastic leukemias is myeloperoxidase or Sudan black B. If the cells are positive then we can exclude ALL. The blasts in this bone marrow, which is the same as that in slide 22, were stained for myeloperoxidase activity. Some but not all myeloblasts will have clusters of granules, while those of monocytic origin will have granules that are scattered and discrete. The cells with heavy granulation are definitely granulocytes, but the two negative cells might be myeloblasts or monoblasts. To distinguish between the two, a stain for nonspecific esterase, such as alpha-naphthyl butyrate or alpha-naphthyl acetate, should be applied. In this case the esterase reaction for monocytes was negative, and the unstained blasts most likely are myeloblasts.
Course Section: 08. Myelocytic Leukemia: Chronic and Acute
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