Megakaryocytic leukaemia as a phase of myeloproliferative disorders

2 cases of megakaryocytic leukaemia are presented as a variant of myeloproliferative disorders. The uncontrolled proliferation of the megakaryocyte-platelet cell line occurred after splenectomy and treatment of blastic phase. Applicability of the term megakaryocytic leukaemia is discussed as well as its relationship to similar disorders. It is suggested that an extensive neoplastic proliferation of megakaryocytes with abnormal maturation and thereby formation of large dysplastic platelets in extramedullary organs especially the liver in the end stage of myelofibrosis is a possible mechanism for this disorder. Treatment with platelet-pheresis may be an effective part of therapy.