CSF2 and acute myeloid leukemia: Administration of granulocyte macrophage colony stimulating factor (GM-CSF) and thrombopoietin (TPO) to patients treated with chemotherapy for AML has been found to cause bone marrow hypercellularity, marked megakaryocytic hyperplasia, megakaryocytic atypia, and reticulin fibrosis with a rapid resolution of the morphologic abnormalities after discontinuation of TPO [8, 9].