Diagnostic criteria for minimally differentiated acute myeloid leukemia (AML-M0). Evaluation and a proposal

We studied immunophenotypic features of 30 cases of minimally differentiated acute myeloid leukemia (AML-M0) using multiparameter flow cytometry and immunohistochemistry and evaluated the immunophenotypic features of previously reported cases to facilitate correct identification of myeloid lineage. All but 1 of our 30 cases expressed CD13 and/or CD33; 2 expressed CD19; 1 expressed CD10; none expressed both CD10 and CD19. Eleven of 30 cases expressed T-cell-associated antigens. All but 2 cases expressed CD34 and/or HLA-DR. Twelve of 27 cases expressed terminal deoxynucleotidyl transferase. Myeloperoxidase (MPO) expression was seen in 22 of 22 cases by immunohistochemistry and 1 of 4 by flow cytometry. None of 27 cases expressed cyCD3 and cyCD79a. We propose following modified criteria for AML-M0: (1) standard criteria for acute leukemia; (2) undetectable or less than 3% MPO or Sudan black B staining in blasts; (3) lack of expression of lymphoid-specific antigens, cyCD3 for T lineage and cyCD79 and cyCD22 for B lineage; and (4) positivity for any of the myelomonocytic lineage antigens known not to be expressed on normal T or B lymphocytes or positivity for MPO as detected by ultrastructural cytochemistry, immunohistochemistry, or flow cytometry.