CD34 and acute myeloid leukemia: The remaining AML samples presented more heterogeneity, which was reflected by the existence of two subclusters, one with overexpression of genes encoding hematopoietic serine proteases, present in azurophil granules of neutrophilic polymorphonuclear leukocytes (AZU1, azurocidin 1, ELANE (previous ELA2), elastase, PRTN3, proteinase 3, and CTSG, cathepsin G), second with upregulation of CD34 antigen, reflecting an early maturation arrest and lack of granulocytic differentiation.