[Classical and molecular cytogenetic abnormalities in 124 pediatric patients with acute lymphoblastic leukemia].

OBJECTIVE

In childhood acute lymphoblastic leukemia (ALL), cytogenetics plays an important role in diagnosis, allocation of treatment and prognosis. On the basis of the conventional cytogenetic analysis, molecular methods have improved pediatric hematologists/oncologist's ability to accurately and rapidly perform risk-stratification on patients with childhood ALL during the last few years. The aim of the present study was to assess the demography of cytogenetic abnormalities in childhood ALL.

METHOD

The study subjects consisted of 124 newly diagnosed ALL patients younger than 16 years of age, who were diagnosed at the Department of Pediatric Hematology/Oncology, Soochow University Children's Hospital. The diagnosis and FAB subtypes of ALL was determined by Wright-Giemsa-stained bone marrow smears and cytochemical staining. Immunophenotyping of the bone marrow samples was performed by flow cytometry. Multiplex polymerase chain reaction (Multiplex PCR) analysis was performed to detect the 29 most common leukemia translocations for routine molecular diagnostic hematopathology practice, and complement the information gained from conventional cytogenetic analysis.

RESULTS

Cytogenetic analysis was successful in 112 of 124 children with ALL. Sixty-eight (60%) of them had clonal chromosomal abnormalities. Numerical imbalances consisted of hyperdiploid (> 47 chromosomes, 36 cases), hypodiploid (< 46 chromosomes, 14 cases), pseudodiploidy (18 cases). Chromosomal translocations were observed in 13 patients by conventional cytogenetic analysis. Three cases were found positive for 4; 11 translocation, 3 cases for 9; 22 translocation, 1 case for 1; 19 translocation and 6 cases for other rare translocations. Multiplex-PCR analysis detected 116 of the 124 ALL patients. Thirteen cases of TEL-AML1, 10 cases of rearrangement in the MLL gene, 4 cases of E2A-PBX1, 4 cases of E2A-HLF, 3 cases of BCR-ABL, 2 cases of TLS-ERG, 32 cases of HOX11 were detected by Multiplex PCR in B-lineage leukemias. SIL-TAL1 had been found in 4 of 7 of T-lineage leukemias.

CONCLUSIONS

Sixty-eight cases of ALL showed chromosomal aberrations. Multiplex PCR positivity was detected in 59 (50%) of the 116 ALL patients studied. Multiplex PCR combined with chromosomal analysis uncovered chromosomal abnormalities in 95 of 124 (77%) of ALL patients and supplemented each other in detecting chromosomal abnormalities.