Transformation of ALL to Acute Mixed Leukemia

Abstract

The case of a 45-year-old male with ALL (L2) who began to have acute mixed leukemia (AMxL) during maintenance chemotherapy, is reported. He had been on the maintenance therapy until March 1987, when he was readmitted to our hospital. On admission the hematological findings were as follows; hemoglobin 11.7 g/dl, platelet count 280×10³/μl and leukocyte count 2.6×10³μl with 4% blasts. The result of bone marrow (BM) aspiration showed that 90% were blasts (20.5% large blasts and 69.5% small blasts) negative for both myeloperoxidase and Sudan black B. Examination of the surface phenotype revealed 61.9% CD19⁺, 36.8% CD10⁺ and 21.7% CD33⁺ cells. After remission reinduction therapy 40% blasts were still present in the bone marrow (22% large blasts and 69.5% small blasts). The blasts were positive for both myeloperoxidase (17%) and Sudan black B (46.5%). Two parameter analysis with FACS revealed that CD33⁺19^- cells were 45.8%; CD33^-19⁺, 15.1%, and CD33⁺19⁺, 2.4%. Those findings indicate that the blasts were composed of two distinct populations of myeloid or lymphoid blast cells. Although gene analysis was not performed, this case was considered to be biclonal rather than biphenotypic AMxL. Then additional chemotherapy was given. However, the small blasts remained at 43.6% in the bone marrow and he died of septicemia in May 1987. Three cases of AMxL transformed from acute leukemia after chemotherapy had been reported in literatures. All of those including our case were resistant to chemotherapy.