An investigation of the t(12;21) rearrangement in children with B-precursor acute lymphoblastic leukaemia using cytogenetic and molecular methods

The t(12;21) is the commonest recurrent translocation in childhood acute ly mphoblastic leukaemia (ALL), the presence of which has been suggested to be a good prognostic feature. We have studied 22 childhood cases of B-precurs or ALL with this rearrangement, and have found no significant differences i n event-free survival between these and a control group of patients with si milar phenotypes. Using a variety of cytogenetic and molecular techniques, we have confirmed a strong association with co-expression of myeloid marker s, frequent deletions of the short-arm of the untranslocated chromosome 12 homologue and duplication of the derivative chromosome 21, Intragenic delet ion of the untranslocated ETV6 gene in 3/12 informative patients points to the likelihood of this gene being a target for deletion.