B-CELL ACUTE LYMPHOBLASTIC LEUKEMIA
The t(9;22)(q34;q11.2) resulting in the Philadelphia (Ph) chromosome is observed in about 5 percent of children ,compared with about 30 percent of adults overall and 50 percent of adults with B-lineage ALL.
The Ph chromosome is the most frequent rearrangement in adult ALL. some patients have had both B-cell and myeloid markers . Because of the high frequency of the BCR/ABL rearrangement and its dire clinical consequences, molecular studies using RT-PCR should be routinely performed at diagnosis when clinical suspicion is high and cytogenetic analysis is nondiagnostic.