[CD7+, CD34+, electronmicroscopically peroxidase-negative acute leukemia transformed from polycythemia vera after 12 years follow-up].

We reported a 72-year-old female patient who developed acute leukemia following a long course of polycythemia vera (PV). For 12 years she had been treated with phlebotomy, nimustine, busulfan, hydroxyurea and irradiation on splenomegaly. In November 1995, her peripheral blood smear showed blast of 30%. Bone marrow blasts were microscopically as well as electromicroscopically peroxidase-negative and CD7 and HLA-DR positive. Six months later, the blasts were positive for CD7, CD34 and HLA-DR. On the basis of morphologic, biochemical and immunophenotypic features, the patient was diagnosed acute leukemia, probably arising at a primitive multipotential stem cell level. She failed to respond to the various combination therapy including prednisolone, vincristine, cytarabine, daunorubicin and etoposide. The stem-cell-leukemia transformation in PV occurs rarely and may be refractory to chemotherapy.