CYTOGENETIC STUDIES IN CHILEAN CHILDREN W ITH ACUTE LYMPHOBLASTIC-LEUKEMIA

Acute lymphoblastic leukemia (ALL) is the most frequent childhood canc er. The leukemic cells of ALL patients,show several well defined numer ic and structural chromosomal abnormalities which are universally know n for its prognostic implications. We studied a group of 44 children w ith ALL, to investigate the incidence of chromosome aberrations in ALL , ifs lymphocyte lineage and some clinical feature associations, and t he finding of non previously described aberrations. A high proportion of patients (79.5%) showed chromosomal abnormalities. Most of them, ha d a pseudodiploid karyotype (46 chromosomes), characterized mainly by a translocation. In relation to chromosome number, 27% of them were hy perdiploid with more than 50; 9% hyperdiploid between 47 - 50 and 7% h ypodiploid (less than 46). Among structural aberrations found, were th e following recurrent translocations: t (1; 19), t (4; 11), t (9; 22) in 6.8%, 9.1% and 2.3% of cases respectively, all related to an early B immunophenotype. Other translocations found, compromised regions 7q2 2, 9p21 - 24. Two new translocations in ALL were found: t (1; 5)(q23; q33), apparently balanced, and t (13; 21)(q14; q22), unbalanced. Other recurrent structural changes found were: deletion (6q), (7q), (9p) (1 1q), (12p) inversion (3q), isochromosome (7q), maker chromosomes and d ouble minutes. The distribution of chromosome abnormalities in this gr oup of patients was in agreement with previous reports from other inve stigators