[Cytogenetic abnormalities in acute lymphoblastic leukemia]

Cytogenetic analysis of blast cells in childhood acute lymphoblastic leukemia has led to the recognition of specific non-random chromosomal abnormalities with prognostic value. Most patients with ALL show karyotype abnormalities, either in chromosome number (ploidy) or as structural changes such as translocations, inversions, or deletions. Many of these chromosomal alterations are associated with specific cytomorphological and immunological types. The greatest impact on patient management has been the finding that the cytogenetic result is an independent prognostic indicator. Certain karyotypes are associated with a favorable prognosis while others indicate a poor outcome. This has led to the administration of alternative therapies according to risk. For instance, hyperdiploidy with a modal chromosome number of 51 or greater, which represents 25-30 % of all cases of ALL, has proved to have the most favorable prognosis among established ploidy groups, whilst translocations such as the Philadelphia translocation t(9;22) and t(4;11) are associated with a poor prognosis. This study focuses on the most important chromosomal abnormalities found in childhood ALL and their prognostic and therapeutic implications.