title: Reassessment of the prognostic significance of hypodiploidy in pediatric patients with acute lymphoblastic leukemia.
abstract: BACKGROUND
  The purpose of the current study was to evaluate the cytogenetic features of the hypodiploid leukemic cells of pediatric patients with this rare subgroup of acute lymphoblastic leukemia (ALL). In addition, the authors determined whether subdivision of the hypodiploid category served a prognostic purpose for these patients.
  
  
  METHODS
  The authors evaluated the cytogenetic records of 979 patients with ALL admitted to St. Jude Children's Research Hospital (Memphis, TN) between 1984 and 1999.
  
  
  RESULTS
  Of 67 patients (6.8%) whose leukemic cells contained a modal number (MN) of chromosomes less than or equal to 45 (i.e., hypodiploid leukemic cells), 57 had an MN of 45 and 10 had an MN of less than 45. In 19 patients, cells with an MN of 45 had a whole chromosome missing (42%), which was a sex chromosome in 12 patients (63%). Leukemic cells with an MN of 45 contained dicentric chromosomes (n = 33) formed from chromosome 9p (55%), 12p (18%), or both (21%). The ETV6-CBFA2 fusion was present in 39% of 28 evaluable B-lineage cases with an MN of 45. The event-free survival rate (EFS) for patients with hypodiploid leukemic cells of MN less than 45 (5-year EFS = 20.0% +/- 10.3%) was significantly (P < 0.001) lower than that for patients with leukemic cells of MN greater than or equal to 45 (5-year EFS = 74.9% +/- 1.6%).
  
  
  CONCLUSIONS
  Low hypodiploidy (MN < 45) should be recognized as a high-risk feature in pediatric ALL. Only two hypodiploid groups (MN < 45 and MN = 45) may be necessary in prognostic assessments.
authors.affiliation: Department of Pathology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105-2794, USA. susana.raimondi@stjude.org
authors.forename: Susana C
authors.initials: SC
authors.lastname: Raimondi
authors.forename: Yinmei
authors.initials: Y
authors.lastname: Zhou
authors.forename: Susan
authors.initials: S
authors.lastname: Mathew
authors.forename: Sheila A
authors.initials: SA
authors.lastname: Shurtleff
authors.forename: John T
authors.initials: JT
authors.lastname: Sandlund
authors.forename: Gaston K
authors.initials: GK
authors.lastname: Rivera
authors.forename: Frederick G
authors.initials: FG
authors.lastname: Behm
authors.forename: Ching-Hon
authors.initials: CH
authors.lastname: Pui
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D002869:Chromosome Aberrations; D002877:Chromosomes, Human / Q000235:genetics; D004171:Diploidy; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000175:diagnosis / Q000235:genetics* / Q000473:pathology; D011237:Predictive Value of Tests; D011379:Prognosis; D015996:Survival Rate