Abstract
In 6 of 20 cases with blast crisis of chronic myelogenous leukemia (CML), predominant proliferation of megakaryocytic series was documented. The megakaryocytic nature of cells in these cases was identified by their morphology, demonstration of platelet peroxidase and demarcation membrane electron microscopically and/or cytoplasmic factor VIII related antigen cytochemically. In one case diagnosed as myelomegakaryoblastic transformation, blasts with various sizes were observed and some of the smaller cells had cytoplasmic blebs. Electron microscopic examination revealed the presence of myeloperoxidase positive myeloblasts as well as platelet peroxidase positive promegakaryolasts. Marrow fibrosis ensued in the later stage. In the other 5 cases proliferation of immature and mature megakaryocytes with atypical features was a prominent finding and in 3 of these cases megakaryoblasts also proliferated, and in the remaining 2 cases myelofibrosis was a predominant feature since early phase of their slowly progressing transformation. Thus, the megakaryocytic transformation of CML encompasses a spectrum of cases characterized by the proliferation of promegakaryoblasts, megakaryoblasts, immature and mature megakaryocytes, associated with varying intensity of marrow fibrosis. Increasing platelet count, fever, bone pain and mass formation sometimes destructing bones appeared to be major manifestation of these cases.
