Characteristics of Acute Myeloid Leukemia without HLA-DR Expression

Abstract

Immunophenotype is one of the most useful tool for the identification of leukemia subtypes [1][2][3][4][5] and can be assigned within a few hours after bone marrow sampling.The typical immunophenotypic feature of acute promyelocytic leukemia (APL) has been reported as CD34-, HLA-DR-, CD13+, and CD33+ [6][7][8]. It has been reported that HLA-DR antigens are consistently negative in APL, whereas the majority of non-APL cases are positive for HLA-DR expression [9,10]; therefore, HLA-DR negativity is known to be useful for distinguishing APL from other AML subtypes, even before the PML-RARA gene rearrangement is identified by cytogenetic or molecular stud- Background : HLA-DR negativity is known to be useful for distinguishing acute promyelocytic leukemia (APL) from other subtypes of AML, but non-APL cases without HLA-DR antigen expression have been reported. The purpose of this study was to evaluate and compare the characteristics of APL, HLA-DR negative non-APL, and HLA-DR positive non-APL cases.Methods : A total of 114 cases of AML admitted at Ewha Womans University, Mokdong Hospital between March 1997 and June 2006 were included in this study. A diagnosis of AML was made based on the results of morphology, cytochemistry, immunophenotype, cytogenetics, and/or fluorescence in situ hybridization.Results : Among the 114 AML patients, HLA-DR antigen was not expressed in 39 (34%), including 24 non-APL (62%) and 15 APL patients (38%). The HLA-DR negative non-APL group showed higher leukocyte counts and positive rate of CD19 expression than did APL group (P<0.05). The remaining laboratory findings were not statistically different between the HLA-DR negative non-APL and APL groups. CD34 expression was more frequent in the HLA-DR positive non-APL group than in the HLA-DR negative non-APL group and APL group. Of the 24 patients with HLA-DR negative non-APL, 7 patients had disseminated intravascular coagulation and 2 patients showed morphologic features similar to those of APL.Conclusions : CD19 expression and leukocyte count may be helpful for differentiating HLA-DR negative non-APL from APL. However, the final diagnosis and classification should be confirmed by cytogenetic or molecular studies. (Korean J Lab Med 2007;27:313-7)

HLA‐DRneg patients without acute promyelocytic leukemia show distinct immunophenotypic, genetic, molecular, and cytomorphologic characteristics compared to acute promyelocytic leukemia

“…These HLA-DR neg non-APL cases (further referred to as DR À AML in contrast to APL and DR þ AML) often resemble cytomorphologic features of hypogranular APL and belong almost exclusively to the myeloid AML subtypes (7,9,16). Published studies comparing APL and DR À AML cases with respect to CD34 expression and lineage infidelity, i.e., detecting the expression of CD2, CD56, CD19, or CD7, reported discrepant results (7,9,(15)(16)(17).…”

“…Published studies comparing APL and DR À AML cases with respect to CD34 expression and lineage infidelity, i.e., detecting the expression of CD2, CD56, CD19, or CD7, reported discrepant results (7,9,(15)(16)(17). Besides the rather small cohorts investigated, these studies also showed profound methodological differences, e.g., in blast gating strategies and in the threshold values used for HLA-DR and/or other antigen expression ranging from 10 to 20% (7,9,(15)(16)(17). Little detailed information about correlations with cytogenetic and novel molecular features are available.…”

“…Besides the 8 to 17% of APL among all patients with AML, an additional 1.2 to 21% of HLA-DR neg AML without the PML-RARa fusion gene have been described (7,9,(15)(16)(17). These HLA-DR neg non-APL cases (further referred to as DR À AML in contrast to APL and DR þ AML) often resemble cytomorphologic features of hypogranular APL and belong almost exclusively to the myeloid AML subtypes (7,9,16).…”

“…These HLA-DR neg non-APL cases (further referred to as DR À AML in contrast to APL and DR þ AML) often resemble cytomorphologic features of hypogranular APL and belong almost exclusively to the myeloid AML subtypes (7,9,16). Published studies comparing APL and DR À AML cases with respect to CD34 expression and lineage infidelity, i.e., detecting the expression of CD2, CD56, CD19, or CD7, reported discrepant results (7,9,(15)(16)(17). Besides the rather small cohorts investigated, these studies also showed profound methodological differences, e.g., in blast gating strategies and in the threshold values used for HLA-DR and/or other antigen expression ranging from 10 to 20% (7,9,(15)(16)(17).…”

Flow cytometric identification of acute myeloid leukemia with limited differentiation and NPM1 type A mutation: a new biologically defined entity

“…5 A variety of previously published data reports on non-APL AML with lack of HLA-DR expression. [6][7][8] Most cases were AML M1/M2 and a high frequency of FLT3-ITD was observed. However, neither a complete and characteristic immuno- Letters to the Editor phenotype nor a clear-cut genetic background has been observed in these studies.…”