Translocation (2;8)(p12;q24) associated with a cryptic t(12;21)(p13;q22) TEL/AML1 gene rearrangement in a child with acute lymphoblastic leukemia

We report a case of childhood acute lymphoblastic leukemia with the simulta neous occurrence of a t(2:8)(p12;q24) typically associated with mature B ce ll or Burkitt leukemia, and a t(12;21)(p13; q22) exclusively associated wit h pre-B cell ALL. The lymphoblasts were characterized as L2 morphology by t he French-American-British classification. However, there were atypical mor pho logic findings for L2 ALL, including vacuolization in some cells. The l ymphoblasts were periodic acid-Schiff positive and myeloperoxidase negative . Immunophenotypic analysis revealed that the majority of lymphoblasts were TdT+. CD10+, CD19+, CD20-. and cytoplasmic mu+ These features were consist ent with an immature pre-B cell leukemia phenotype with some characteristic s of a mature B-cell leukemia. A t(2;8)(p12;q24)(p12;q24), characteristic o f mature B-cell leukemia or Burkitt type leukemia, was detected by conventi onal cytogenetics with no other cytogenetic abnormalities. However, diagnos tic peripheral blood and bone marrow specimens demonstrated simultaneous oc currence of a cryptic t(12;21)(p13:q22) by both FISH and RT-PCR. The simult aneous occurrence of these translocations in a pediatric patient have impli cations for the pathogenesis of leukemias with t(2;8)(p12;q24) as well as 1 (12;21)(p12;q22). Analysis of additional cases of leukemia with translocati ons involving the MYC locus on 8q24 will be required to determine the frequ ency of association with the cryptic t(12;21)(p13;22), and the prognostic s ignificance of the simultaneous occurrence of the translocations. (C) 2000 Elsevier Science Inc. FLU rights reserved.