CSF2 and acute myeloid leukemia: Administration of granulocyte macrophage colony stimulating factor (GM-CSF) in combination with thrombopoietin (TPO) to patients who had received chemotherapy for acute myeloid leukemia (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.