T-Cell-Associated Fluorescence In Situ Hybridization (FISH) Probes May Help Distinguish between T Lymphoblastic Leukemia (T-LBL) and Acute Myeloid Leukemia with T-Cell Antigen Expression (AML-T)
DS Bosler, CA Hanson, RA Knudson, RP Ketterling, JD Hoyer. Cleveland Clinic, Cleveland, OH; Mayo Clinic, Rochester, MN
Background: The diagnostic distinction between T-LBL and AML can be challenging, as co-expression of both myeloid and T-cell associated antigens can be found in both leukemias. Our study evaluated the potential diagnostic role of various T-cell-associated FISH probes in the evaluation and classification of T-LBLs and AMLs.
Design: We identified 145 acute leukemias (75 T-LBL, 70 AML) with diagnostic flow cytometry and available cell pellets for FISH studies. 28 of 75 T-LBLs had at least one myeloid antigen expressed. AMLs selected were either "with minimal differentiation" or "without maturation"; 43 of 70 AMLs had expression of T-cell associated antigen(s). FISH probes used included: SIL/TAL1 (1p32), HOX11L2/BCL11B, t(5;14)(q35;q32), and also break apart probes for T-cell receptor α/δ(TCR-AD) (14q11.2), and T-cell receptor β (TCR-B) (7q34). Histograms (for T-LBL and AML-T) and cytogenetic karyotypes were reviewed when available.
Results: At least one FISH abnormality was identified in 35 (47%) of 75 T-LBLs. A TCR-AD split was the most frequent abnormality detected (19/75, 25%), and 5/75 (7%) T-LBLs had more than one abnormality identified by FISH. There were no reliable differences in the abnormalities detected by FISH in the T-LBLs that had myeloid antigens expressed versus those that did not. No T-cell FISH abnormalities were identified in any of the 70 AML cases, regardless of T-cell antigen expression.
|% Any FISH Abnl||% >1 FISH Abnl||% TCRAD||% TCRB||% SIL/TAL||% HOX11L2/ BCL11B|