Ultrastructural aspects of megakaryocyte/platelet system in essential thrombocythemia.

Six cases of essential thrombocythemia (ET) have been investigated in bone marrow as well as in blood cells. In majority of the cases, the bone marrow aspirate was hypercellular and presented an increased number of megakaryocytes, some of them with displastic appearance. The ultrastructural pattern of platelet peroxidase permitted us to identify atypic megakaryocytes and megakaryoblasts, particularly when present in pheripheral blood.