HIGH-RATE OF CHROMOSOME-ABNORMALITIES DETECTED BY FLUORESCENCE IN-SITU HYBRIDIZATION USING BCR AND ABL PROBES IN ADULT ACUTE LYMPHOBLASTIC-LEUKEMIA

The value of dual-color fluorescence in situ hybridization (FISH) with BCR and ABL probes for the detection of the Philadelphia (Ph) translo cation and of other alterations involving ABL and/or BCR was evaluated in adult acute lymphoblastic leukemia (ALL). One hundred and four pat ients were studied prospectively using interphase nuclei FISH, chromos ome analysis (CA), and PCR assays for the chimeric BRC/ABL transcript. FISH detected a Ph translocation in 24 cases (23.1%), as was confirme d by CA and/or PCR. FISH revealed a false positive diagnosis of a Ph t ranslocation in four cases (5% false positive rate). Among 54 cases wi th combined FISH, CA and PCR assays, FISH failed to establish a correc t diagnosis in 3.7%, PCR in 5.6%, and CA in 7.4%. The combination of t wo screening methods led to discrepant results in 9.3% (FISH + PCR), 1 1.1% (FISH + CA), or 13% (CA + PCR) of the cases. In seven of 80 (8.8% ) Ph-negative patients, gain of BCR and/or ABL was identified. Overall , FISH detected alterations of the BCR and/or ABL genes with an incide nce of 29.8% of the current study. Due to the possibility of false pos itive diagnosis of a Ph translocation using dual-color FISH the combin ation with chromosome and/or RT-PCR analyses is recommended in adult A LL patients.