Leukemia with megakaryocytic differentiation following essential thrombocythemia and myelofibrosis. Case report and review of the literature.

Leukemias of megakaryocytic lineage are rare and heterogeneous clinical entities. The nomenclature published in the literature is confusing and perhaps inappropriate to designate these primary myeloproliferative disorders. We describe a patient with essential thrombocythemia who evolved through myelofibrosis and myeloid metaplasia to a final picture of leukemia with megakaryocytic differentiation in the peripheral blood. This case illustrates different aspects of a chronic myeloproliferative disorder where myelofibrosis and myeloid metaplasia are frequent but secondary events. We have reviewed the literature focusing on the role of clonal megakaryocytic proliferation in myelofibrosis and on the clinical characterization of leukemias with megakaryocytic phenotype. We also present our interpretation of the literature which indicates that a formal review of the nomenclature is urgently needed.