AML with minimal differentiation

At least 20% nongranular blasts in blood or bone marrow. Usually blasts are middle sized, have a round or slightly indented nuclei with dispersed chromatin, one or two nucleoli, varying degree of basophilic cytoplasm and no Auer rods.
Rarely small blasts with condensed chromatin and scant cytoplasm that may resemble lymphoblasts.
The blasts are Sudan Black negative, usually express CD34, CD13 and/or CD117, CD33 expression is variable, MPO is negative.