[1162] Correlation of Flow Cytometry (FC) and Fluorescence In-Situ Hybridization (FISH) in Precursor T-Cell Lymphoblastic Leukemia (T-ALL)

DS Bosler, CA Hanson, RA Knudson, RP Ketterling, JD Hoyer. Mayo Clinic, Rochester, MN

Background: T-ALL is phenotypically diverse. CD7 and c-CD3 are uniformly expressed, while expression of other T-cell markers varies, and myeloid or B-cell antigen expression can present diagnostic challenges. Integrating genetic findings provides additional information and may help clarify lineage in these cases. The aim of our study was to correlate FC and FISH findings in T-ALL.
Design: We identified 64 T-ALL cases with diagnostic FC and concurrent archived cell pellets for FISH. Histograms were reviewed when available. FISH performed included: SIL/TAL1 (1p32), TCRAD (14q11.2), p16/D9Z1 (9p21), BCR/ABL, t(9;22)(q34;q11.2) dual fusion (D-FISH), MLL (11q23), HOX11L2/BCL11B, t(5;14)(q35;q32) DFISH, TCRB (7q34), and AF10/PICALM, t(10;11)(p13;q13) DFISH.
Results: c-CD3, TdT, CD5 and CD7 were almost always uniformly expressed, while CD2 (77%), s-CD3 (42%), CD10 (48%), CD34 (32%), HLA-DR (18%), and CD56 (23%) were each expressed in some cases. Dual CD4/CD8 positivity (54%) and CD4/CD8 negativity (20%) were also prevalent. CD13 was expressed in 27%, CD33 in 15%, CD15 in 13% and CD117 in 21%. At least 2 myeloid markers were coexpressed in 18%. Of cases expressing a myeloid antigen, 70% were s-CD3 negative.

	% FISH Pos	% CD2 Pos	% s-CD3 Pos	% CD4/8 Dual Pos
All Cases	72	77	42	54
TCRAD	25	94	40	80
TCRB	6	100	75	100
p16	41	92	50	63
SIL/TAL	13	100	63	40
TCRAD,TCRB,p16,SIL/TAL Neg	-	64	32	46

TCRAD, TCRB, p16 and SIL/TAL positivity was more likely to be associated with CD2 and s-CD3 expression compared to other cases. CD4/CD8 expression was slightly more common in TCR rearranged cases.

CD10 was expressed more often in TCRAD (73%) and ABL (80%) cases. While TCRAD and TCRB often coexisted with p16 loss (75% and 100%), MLL (8% of cases) was always a sole abnormality, and was associated with CD34 (60%). FISH and cytogenetics (CG) were concordant in 65% of cases, with FISH positive/CG negative (30%) > CG positive/FISH negative (5%). No differences in age or WBC count were observed between various FISH findings.
Conclusions: CD5 and CD7 are the most consistently expressed T-cell markers in T-ALL, while s-CD3 is expressed in <50%. TCR rearranged T-ALL correlates with CD2, s-CD3 and dual CD4/CD8 expression. FISH abnormalities are present in 72% of cases, 39% of which have normal karyotypes, making FISH a useful adjunct to CG. In cases with myeloid and T-cell marker expression, FISH abnormalities may provide potentially useful complimentary information.
Category: Hematopathology

Wednesday, March 11, 2009 1:00 PM

Poster Session VI # 176, Wednesday Afternoon