[1423] CD34-HLA-DR- Is Most Commonly Seen in Children with Acute Megakeryoblastic Leukemia in Addition to Acute Promyelocytic Leukemia: A Potential Diagnostic Pitfall

Kevin Lee, Amy McGranahan, Tyler T Winkler, Xiayuan Liang. Children's Hospital Colorado, Aurora, CO; University of Colorado Denver School of Medicine, Aurora, CO

Background: The pattern of CD34-HLA-DR- is one of important features in acute promyelocytic leukemia (APL). This pattern occasionally is seen in other types of acute myeloid leukemia (AML). Acute megakaryoblastic leukemia (AMKL) is characterized by expression of CD61/CD41/CD42 and frequently shows non-typical morphology. In most institutions, CD61, CD41 or CD42 is not included in the regular AML panel. When CD34-HLA-DR- with lack of MPO occurs, it is frequently interpreted as an undifferentiated leukemia or sometimes acute lymphoblastic leukemia (ALL) if blasts aberrantly express lymphoid markers. We have noticed that in addition to APL, CD34-HLA-DR- appears to be more often seen in AMKL than other types of AML in children. To prove our hypothesis, we studied a series of 98 cases of non-APL AML to investigate the difference of frequency of antigen expression between AMKL and other types of AML.
Design: 98 cases of newly diagnosed non-APL AML (11 AMKL and 87 other types of AML) at Children's Hospital CO were evaluated. Immunophenotype was performed by flow cytometry. Positive expression is defined as expression of a marker in ≥20% of blasts according to the criteria of the Children's Oncology Group.
Results: 1) The frequency of CD34-HLA-DR- or HLA-DR- was significantly higher in AMKL than other types of AML. 2) AMKL showed loss of some myeloid associated antigens (CD11c, CD15, and CD33) in a significant number of cases compared with other types of AML. 3) AMKL aberrantly expressed CD7 and CD56 more often than other types of AML.

Non-APL AMLCD34-HLA-DR-HLA-DR-CD11c+/CD13+CD15+/CD33+CD117+/CD56+CD2+/CD7+CD19+/CD20+
AMKL50% (5/10)100% (11/11)16.7% (1/6)/60% (6/10)0% (0/11)/54.6% (6/11)90.9% (10/11)/72.7% (8/11)0% (0/9)/50% (5/10)10% (1/10)/0% (0/11)
Other types of AML9.2% (8/87)15.1% (13/86)67.6% (50/74)/80.5% (70/87)62.3% (43/69)/91.9% (80/87)63.9% (46/72)/35.4% (28/79)3.5% (3/85)/18.8% (16/85)12.9% (11/85)/0% (0/83)
p value0.00340.00010.0217/0.21610.0001/0.00360.0933/0.02391.000/0.03941.000/1.000

Conclusions: 1) In non-APL AML patients, when CD34-HLA-DR- or HLA-DR- is present, the immunophenotype panel should include megakaryocytic markers in order to avoid overlooking the possibility of AMKL. 2) More frequent loss of myeloid associated antigens (CD11c, CD15, and CD33) and expression of T/NK cell markers (CD7 and CD56) in AMKL suggest that AMKL may have weaker myeloid differentiation and be more easily impinged upon by other lineages than other types of AML.
Category: Hematopathology

Tuesday, March 5, 2013 9:00 AM

Proffered Papers: Section C, Tuesday Morning


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