| Summary: | Acute promyelocytic leukemia (APL) is a subtype of acute myeloid leukemia (AML) in which abnormal promyelocytes predominate. APL is rare in children (approximately 10% of childhood AML) and is characterized by a higher incidence of hyperleukocytosis, an increased incidence of microgranular morphology, the presence of balanced t(15;17)(q22;q11.2-12) translocation, and more frequent occurrence of the PML-RARα isoforms bcr 2 and bcr 3 compared to adults. The cytomorphology of microgranular variant blasts is obviously different from AML M3 blasts; these cells have a nongranular or hypogranular cytoplasm or contain fine dust-like cytoplasmic azurophil granules that may not be apparent by light microscopy. This case report emphasizes the importance of a high index of suspicion for the diagnosis of APL, the hypogranular variant in particular. They are responsive to differentiation therapy with all trans-retinoic acid and complete remission in seen in >80% cases.
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