Circulating micromegakaryocytes signaling blast transformation of chronic myeloid leukaemia.

A patient with chronic myeloid leukaemia had numerous micromegakaryocytes in the peripheral blood and bone marrow appearing coincidentally with the onset of blast crisis. These cells were initially confused with lymphocytes because of their size, configuration and scanty cytoplasm. The true identification of these cells can be suspected by careful scrutiny of well prepared Wrights stained preparations and proven electronmicroscopically. Such marked dysplasia of the megakaryocyte series appears to be a poor prognostic sign in chronic myeloid leukaemia.