Morphologic Evidence of in vivo Differentiation in Acute Myeloblastic Leukemia

Gönül Hiçsönmez, MD, Hacettepe Children’s Hospital, Department of Pediatric Hematology, TR-06100 Ankara (Turkey) Differentiation of myeloid leukemic cells to mature granulocytes by high-dose methylprednisolone (HDMP; 20-30 mg/kg/day) treatment with remarkable antileukemic effect have been shown by us in children with acute myeloblastic leukemia (AML) [1-5]. It has also been shown that certain steroid hormones (prednisolone and dexa-methasone) are among the most potent differentiating agents and can induce differentiation of some mouse myeloid leukemic cells to macrophages and granulocytes [6-8]. Combined HDMP with cyto-toxic chemotherapy increased the remission rate and prolonged the duration of remission in children with AML [9]. Recently Hamidah et al. [10] documented in vivo evidence of differentiation by all-trans retinoic acid in a case of acute promyelocytic leukemia which was characterized by cytoplasmic vacuolation in the neutrophils. We would like to report similar morphologic findings observed during HDMP treatment in a child with AML. A 1-year-old girl was admitted with orbito-ocular granulocytic sarcoma and a generalized nodular leukemic infiltration of the skin. Complete blood count showed Hb 9.8 g/dl, WBC 80 × 1071 with 58% blasts and normal platelet count. The bone marrow aspirate was cellular and 35% of the cells were blasts with prominent cytoplasmic vacuolations (fig. la). Histochemical examination revealed that the blasts were positive for peroxidase and weakly PAS positive. The vacuoles did not stain. Fifty-six percent of the marrow blasts were CD13 positive, 20% CD34 positive, 16% CD14 positive, 50% CD19 positive and they were TdT, CD2 and CD10 negative (0%). Induction therapy was begun with oral methylprednisolone at a daily dose of 30 mg/kg. A significant decrease in the circulating blast cell count was noted 2 days after HDMP treatment, however, the WBC count increased to 100 × 1071. Because of the increase in the WBCs, possibly due to HDMP effect [2], mitoxantrone 10 mg/m2, vin-cristine 0.05 mg/kg and daunomycin 1 mg/kg were added to HDMP treatment on day 3. Four days after initiation of HDMP treatment, the blast cells disappeared from the peripheral blood and numerous abnormally nucleated neutrophils which contained multiple vacuola»