The "typical" immunophenotype of acute promyelocytic leukemia (APL-M3): Does it prove true for the M3-variant?

The immunophenotypes of 12 acute promyelocytic leukemias (APL-M3; eight hyp ergranular, four microgranular) with documented PML-RAR-alpha fusion gene a re presented. Bone marrow mononuclear cells were immunophenotyped using a p anel of 20 monoclonal antibodies. The hypergranular APLs exhibited a mature myeloid phenotype as it has been described to be typical for M3. No lineag e infidelity was detectable in classic M3 cases. In contrast, among the fou r cases of M3 variant, all leukemias showed marked expression of CD34 and t wo of four cases expressed the HLA-DR antigen. The CD2 antigen was expresse d in three of four cases. Furthermore, one case showed expression of the CD 56 antigen, and one case was positive for the blood group H antigen. The da ta suggest that microgranular APL is a heterogeneous entity with regard to the immunologic phonotype. Cytometry (Comm. Clin. Cytometry) 42:106-109, 20 00. (C) 2000 Wiley-Liss, Inc.