Cytogenetic findings in childhood acute lymphoblastic leukemia.

Chromosome studies were performed on the bone marrow cells of 42 children with newly diagnosed acute lymphoblastic leukemia (ALL). All the children were subsequently treated with the same protocol. Chromosomal abnormalities were found in 25 patients, i.e., in 59.5% of the cases. Hyperdiploidy was observed in 21.4% hypodiploidy in 14.3%, and pseudodiploidy in 23.8% of the children. The most frequent structural aberrations were translocations, which were found in half of the patients with abnormal karyotypes. Chromosomes #5, #6, #7, #9, #14, #17, and #21 were involved in different types of changes most frequently. Because these findings correspond with observations published by others, they can be regarded as evidence of nonrandom involvement of these chromosomes in rearrangements in ALL. Special attention should be also paid to the deletion of 6q, which seems to be relatively common in ALL. In 12 cases, clonal evolution of karyotypic changes was observed.