Cytogenetic, cytomorphologic, and immunologic analysis in 55 children with acute lymphoblastic leukemia.

This paper presents the results of cytogenetic analysis in 55 children with acute lymphatic leukemia (ALL). Acquired chromosome aberrations were identified in 35 (63.6%) children. Difference in frequency of clonal aberrations depending on age of patients was observed. Thus, acquired aberrations were detected in all three children up to 6 months of age, in 57.8% in the group from 1-10 years, and in six (85.7%) of seven children older than 10 years of age at diagnosis. The analysis revealed chromosome aberrations specific for ALL. Hyperdiploidy >50 was identified in 20% of children, and the association with CALLA+ early pre-B and L2-ALL was observed. del(6) and t(1;19) were identified in 7.3% and 5.5% of children, respectively. No association with a specific morphology or specific immunophenotype for both structural aberrations has been established. The association of structural aberrations involving regions 14q11-12 and T-cell ALL, however, has been observed, as an aberration was identified in two (3.6%) children, i.e., in 25% of our T-cell leukemias. Interstitial deletion of the long arm of chromosome 13, a rare chromosomal aberration in ALL, was identified in addition to del(9)(q31) in a 17-month-old girl with constitutional trisomy of chromosome 21 and B-cell ALL-L2. Interesting is the finding of hyperdiploidy with 52 chromosomes and structural aberrations of chromosome 1 in a 1-month-old girl with morphologically unclassified CALLA+ pre-T acute leukemia. To our knowledge this is the first case of hyperdiploidy >50 in a neonatal leukemia.