Acute promyelocytic leukemia is characterized by the presence of atypical promyelocytes in bone marrow and peripheral blood. Neoplastic promyelocytes, which often have Auer rods, are most commonly seen in early myeloid precursors in certain subtypes of myeloid leukemia.
A 63-year-old male patient,was admitted to our clinic with the complaints of malaise and weight loss for several months, presented with leucopenia and mild anemia. There were no findings of organomegaly, lymphadenopathy and bleeding diathesis and no evidence of infection. Bone marrow aspiration and biopsy which was performed with the preliminary diagnosis of myelodysplastic syndrome revealed a slightly increased Myeloid/Erythroid ratio, distinct maturation arrest in the cells of myeloid lineage 15-20% of which have nucleocytoplasmic asynchrony, course cytoplasmic granules and Auer rods. Auer rods were also present in the cytoplasm of mature neutrophils. Additionally, megakaryocytes were also dysplastic. The immunohistochemical staining was positive for CD117 in 10% of the cells and there was no staining for CD34. The diagnosis was obscure until the fluorescein in situ hybridization results which was positive for PML-RARa fusion t(15;17) (q24.1;q21.2) was received. The patient was eventually diagnosed with acute promyelocytic leukemia.
This unusual case of APL was characterized with rarity of atypical promyelocytes in the bone marrow, distinct dysplasia in the myeloid and megakaryocytic lineages and silent clinical course without coagulopathy which caused delay in diagnosis, and well response to treatment.
Key words: acute promyelocytic leukemia, auer rods, mature neutrophils
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