BCR rearrangement without juxtaposition of ABL in pre-T acute lymphoblastic leukaemia.

The incidence and clinical relevance of the Philadelphia (Ph) translocation t(9:22) (q34:q11) in T-lineage acute lymphoblastic leukaemia (ALL) are unknown. We describe a patient with pre-T-ALL and a clonal 22q-aberration detected by conventional cytogenetics, suggestive of a Ph translocation. However, fluorescence in situ hybridization (FISH) using BCR and ABL probes revealed a translocation with one breakpoint within the BCR gene on chromosome 22 without juxtaposition of ABL on chromosome 9. We discuss the diagnostic and possible pathogenetic implications of this Ph-like chromosomal aberration.