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The "typical" immunophenotype of acute promyelocytic leukemia (APL-M3): does it prove true for the M3-variant?
M Exner1, R Thalhammer, S Kapiotis
1Department of Laboratory Medicine, University of Vienna, Austria.
Abstract:
The immunophenotypes of 12 acute promyelocytic leukemias (APL-M3; eight hypergranular, four microgranular) with documented PML-RAR-alpha fusion gene are presented. Bone marrow mononuclear cells were immunophenotyped using a panel of 20 monoclonal antibodies. The hypergranular APLs exhibited a mature myeloid phenotype as it has been described to be typical for M3. No lineage infidelity was detectable in classic M3 cases. In contrast, among the four cases of M3 variant, all leukemias showed marked expression of CD34 and two of four cases expressed the HLA-DR antigen. The CD2 antigen was expressed in three of four cases. Furthermore, one case showed expression of the CD56 antigen, and one case was positive for the blood group H antigen. The data suggest that microgranular APL is a heterogeneous entity with regard to the immunologic phenotype.
Insights
This study examined acute promyelocytic leukemia (APL) immunophenotypes. Microgranular APL variants showed diverse immune markers, unlike typical hypergranular APL, suggesting heterogeneity.
Area of Science:
- Hematology
- Immunology
- Oncology
Background:
- Acute promyelocytic leukemia (APL) is a subtype of acute myeloid leukemia.
- APL is characterized by the PML-RAR-alpha fusion gene.
- Immunophenotyping aids in classifying leukemia subtypes.
Purpose of the Study:
- To present the immunophenotypes of 12 acute promyelocytic leukemias (APL-M3) with the PML-RAR-alpha fusion gene.
- To compare the immunophenotypic profiles of hypergranular APL and microgranular APL variants.
Main Methods:
- Immunophenotyping of bone marrow mononuclear cells from 12 APL patients.
- Utilized a panel of 20 monoclonal antibodies.
- Analyzed expression of various cell surface antigens.
Main Results:
- Hypergranular APL cases displayed a mature myeloid phenotype, consistent with M3 classification.
- Microgranular APL variants showed immunophenotypic heterogeneity.
- Microgranular APL cases frequently expressed CD34, HLA-DR, and CD2 antigens.
Conclusions:
- Microgranular APL represents a heterogeneous entity.
- Immunophenotypic differences exist between hypergranular and microgranular APL subtypes.
- Further investigation into microgranular APL immunophenotypes is warranted.
