Acute megakaryocytic leukemia in essential thrombocythemia: an unusual evolution?

Essential thrombocythemia (ET) is a chronic myeloproliferative disorder that can rarely undergo leukemic transformation either in treated (3-7%) or untreated patients (1%). Evolution to myeloblastic or myelomonoblastic acute leukemia is commonly described in the literature, whereas lymphatic and megakaryocytic forms are considered unusual. Here, we report three cases of acute megakaryocytic leukemia (LMA-M7) among 11 acute leukemic transformations observed in our series of 321 ET patients. LMA-M7 was diagnosed employing immunophenotyping according to FAB criteria. These recurrences of LMA M7 suggest that this kind of evolution cannot be considered rare or casual in ET.