title: Mixed lineage leukemia-rearranged childhood pro-B and CD10-negative pre-B acute lymphoblastic leukemia constitute a distinct clinical entity.
abstract: OBJECTIVE
  Mixed lineage leukemia (MLL) abnormalities occur in approximately 50% of childhood pro-B acute lymphoblastic leukemia (ALL). However, the incidence and type of MLL rearrangements have not been determined in common ALL (cALL) and CD10+ or CD10- pre-B ALL.
  
  
  METHODS
  To address this question, we analyzed 29 patients with pro-B ALL, 11 patients with CD10- pre-B ALL, 23 pre-B, and 26 cALL patients with CD10 on 20% to 80%, as well as 136 pre-B and 143 cALL patients with CD10 > or = 80% of blasts. They were all enrolled in four Austrian ALL multicenter trials. Conventional cytogenetics were done to detect 11q23 abnormalities and in parallel the potential involvement of the MLL gene was evaluated with a split apart fluorescence in situ hybridization probe set.
  
  
  RESULTS
  We found that 15 of 29 pro-B ALL, 7 of 11 CD10- pre-B ALL, and 1 of 2 French-American-British classification L1 mature B-cell leukemia cases had a MLL rearrangement. However, no 11q23/MLL translocation was identified among the CD10+ pre-B and cALL patients. MLL-rearranged pro-B and CD10- pre-B ALL cases had similar clinical and immunophenotypic (coexpression of CDw65 and CD15) features at initial diagnosis.
  
  
  CONCLUSIONS
  The striking similarities between the two CD10- ALL subsets imply that CD10- pre-B ALL variants may represent pro-B ALL cases that maintained the propensity to rearrange and express their immunoglobulin heavy chain rather than actual pre-B ALL forms transformed at this later stage of B-cell differentiation. However, direct experimental data are needed to confirm this observation.
authors.affiliation: Department of Hematology and Oncology, St. Anna Children's Hospital, Vienna, Austria.
authors.forename: Andishe
authors.initials: A
authors.lastname: Attarbaschi
authors.forename: Georg
authors.initials: G
authors.lastname: Mann
authors.forename: Margit
authors.initials: M
authors.lastname: König
authors.forename: Manuel
authors.initials: M
authors.lastname: Steiner
authors.forename: Sabine
authors.initials: S
authors.lastname: Strehl
authors.forename: Anita
authors.initials: A
authors.lastname: Schreiberhuber
authors.forename: Björn
authors.initials: B
authors.lastname: Schneider
authors.forename: Claus
authors.initials: C
authors.lastname: Meyer
authors.forename: Rolf
authors.initials: R
authors.lastname: Marschalek
authors.forename: Arndt
authors.initials: A
authors.lastname: Borkhardt
authors.forename: Winfried F
authors.initials: WF
authors.lastname: Pickl
authors.forename: Thomas
authors.initials: T
authors.lastname: Lion
authors.forename: Helmut
authors.initials: H
authors.lastname: Gadner
authors.forename: Oskar A
authors.initials: OA
authors.lastname: Haas
authors.forename: Michael N
authors.initials: MN
authors.lastname: Dworzak
mesh_terms: D000293:Adolescent; D001402:B-Lymphocytes; D002648:Child; D002675:Child, Preschool; D002869:Chromosome Aberrations; D005260:Female; D006801:Humans; D007143:Immunoglobulin Heavy Chains; D016130:Immunophenotyping; D017404:In Situ Hybridization, Fluorescence; D007223:Infant; D008297:Male; D051788:Myeloid-Lymphoid Leukemia Protein / Q000235:genetics*; D015260:Neprilysin; D010641:Phenotype; D015452:Precursor B-Cell Lymphoblastic Leukemia-Lymphoma / Q000145:classification / Q000235:genetics*; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000145:classification / Q000235:genetics*; D011379:Prognosis; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
chemical_list: D007143:Immunoglobulin Heavy Chains; D051788:Myeloid-Lymphoid Leukemia Protein; D015260:Neprilysin