[1399] Acute Myeloid Leukemia with Minimal Differentiation: Immunophenotypic, Cytogenetic and Molecular Features of 50 Cases

T Muzzafar, FA Khokhar, CE Bueso-Ramos, LJ Medeiros. UT MD Anderson Cancer Center, Houston, TX; Elizabeth Hospital, Beaumont, TX

Background: Acute myeloid leukemia with minimal differentiation (FAB: AML M0) has no evidence of myeloid differentiation by morphology and routine cytochemistry and has poor prognosis. The goal of this study was to review features of AML M0 as per age at presentation.
Design: 50 cases of AML-M0 were identified in our files for 2004-2008. All cases were analyzed by cytochemistry, flow cytometric immunophenotyping (FCI), conventional cytogenetics and molecular studies. Cases were divided into two groups by age (<60 & >60 yr).
Results: Cases included 32 males and 18 females with median age of 67 (range 16-87) yr. 18 patients were less than and 32 were greater than 60 yr. Median peripheral blood (PB) and bone marrow blasts were 22% and 67% respectively.

Immunophenotypic, cytogenetic and molecular findings in 50 cases of AML-M0
MPO 16% (6/37)CD34 93% (43/46)CD117 98% (47/48)HLA-DR 95% (41/43)CD13 91% (41/45)CD15 72% (13/18)CD33 90% (43/48)TdT 25% (10/40)
B-cell markers 15% (6/39)T-cell markers 27% (9/33)FLT3 9% (4/44)RAS 13% (5/38)c-KIT 0% (0/15)NMP 0% (0/2)RUNX-1 0% (0/4)JAK2 0% (0/4)
IgH 29% (2/7)TCR-γ 40% (4/10)TCR-β 0% (0/3)Abnormal karyotype 76% (38/50)Complex karyotype 26% (13/50)
Cases expressing B- or T-cell antigens did not meet criteria for mixed phenotype acute leukemia, NOS

Cytogenetic and molecular findings in 50 cases of AML-M0 by age
Age (years)Chr 5Chr 7Chr 17Complex karyotypeTrisomiesPB Blasts %
<60 (n = 18)39% (7/18)44% (8/18)33% (6/18)50% (9/18)6% (1/18)72
>60 (n = 32)22% (7/32)19% (6/32)3% (1/32)12% (4/32)28% (9/32)23

Patients <60 years old had higher frequency of -17, complex karyotype [Fischer's exact test] and a higher peripheral blast %age [Student's t test] than patients >60 years old. Differences in abnormalities of chr 5, 7, trisomies & TdT were not statistically significant. All cases with +13 had TdT expression; 25% (1/4) of these cases had FLT3 ITD mutations.
Conclusions: Patients with AML-M0 <60 years old are more likely to have del 17, complex karyotype, trisomies and higher PB blast percentage than patients > 60 years old. Del 17, which is known to be a negative prognostic marker, was present in 33% of these cases; a far higher proportion than the 5% reported in recent unselected large series of AML.
Category: Hematopathology

Wednesday, March 24, 2010 1:00 PM

Poster Session VI # 184, Wednesday Afternoon


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