Dysmegakaryopoiesis resembling acute megakaryoblastic leukemia in treated acute myeloid leukemia

Acute myeloid leukemia (AML) is characterized by trilineage dysplasia, including atypical megakaryocytes. Acute megakaryoblastic leukemia (FAB M7) is particularly associated with atypical megakaryocytic hyperplasia (AMH). Fifteen patients with nonmegakaryoblastic AML developed AMH after therapy, comprising 12.6% of cases of AML diagnosed from 1986 to 1989. Platelet counts were normal in nine patients and decreased in six. Blasts comprised less than 5% of cells in 40% of the biopsies, ranged from 5-15% in 53%, and comprised more than 30% of cells in 7%. Numerous small hypo- and hyperlobated megakaryocytes were seen in all specimens, often occurring in clusters, and were more easily seen in sections than in smears. Subsequent biopsies in 13 patients showed a remission marrow in seven, increased blasts in three, and AML in three; none showed AMH. AMH resembling acute megakaryoblastic leukemia may be seen transiently after treatment of AML.