Malignant disorders of megakaryocytes.

Among hematologic malignancies, there are three disorders whose behavior is governed principally by the abnormal proliferation of a malignant megakaryocytic clone or a product thereof. These disorders are essential thrombocythemia, agnogenic myeloid metaplasia, and acute megakaryoblastic leukemia. Although there are other myeloproliferative diseases that can have high platelet counts, the major pathobiology of those diseases most commonly results from the proliferation of other hematopoietic lineages. Despite the rarity of the three disorders of malignant megakaryopoiesis mentioned above, advances have been made in the diagnosis, prognosis, and treatment of these disorders in recent years. However, understanding of the cellular and especially molecular pathobiology lags far behind.