Megakaryoblastic termination of myeloproliferative disorders.

: Megakaryoblastic termination of myeloproliferative disorders is rare. The morphology of megakaryoblastic transformation can be subtle and is often mistaken for myeloid or lymphoid proliferations. Previously reported observations suggest a relatively poor prognosis for this category of patients, making precise diagnosis imperative. A multifaceted approach using morphology, ultrastructure, cytochemistry, and immunological membrane analysis may be helpful. We present two cases of myeloproliferative disorder with aggressive megakaryoblastic phases (myelofibrosis with agnogenic myeloid metaplasia and chronic myeloid leukemia with blast crisis). The clinical course is described and the results of the morphological, cytochemical, ultrastructural, and cytogenetic studies of both cases are presented. In addition, immunochemical studies (flow cytometry) and platelet function studies (aggregation, beta-thromboglobulin, and platelet factor IV release) were done for one of these patients.