Childhood B-cell acute lymphoblastic leukemia with FAB-L1 morphology and a t(9;11) translocation involving the MLL gene.

The t(9;11) (p21-22;q23) translocation is frequently associated with acute monoblastic leukemia but may occasionally be seen in patients with acute lymphoblastic leukemia (ALL). We report a case of childhood ALL associated with t(9;11) (p21-22;q23) as the unique recurring chromosomal abnormality. A 3-month-old girl presented with "lymphomatous" ALL (renal enlargement), a high leukocyte count and central nervous system (CNS) involvement. Leukemic cell typing revealed a sIg+ B-cell immunophenotype without CD10 and CD34 antigenic expression while the blast cell morphology was of the FAB-L1 type. Splitting of a YAC encompassing the MLL gene was shown by fluorescence in situ hybridization (FISH) studies of the patient's metaphase chromosomes. Rearrangement of the MLL gene was confirmed by Southern blot analysis. Despite treatment with an hyperintensive polychemotherapeutic regimen, the patient achieved a complete remission but relapsed 9 months later. These results provide further evidence that the t(9;11) may be observed in ALL, involves the MLL gene and is associated with a poor outcome. Moreover, this observation clearly illustrates that sIg+ B-cell ALL is not necessarily associated with a Burkitt (L3) morphology.