Detection of t(12;21) in childhood acute lymphoblastic leukemia by fluorescence in situ hybridization

Metaphase preparations from 36 patients with acute lymphoblastic leukemia ( ALL) have been retrospectively screened by fluorescence in situ hybridizati on (FISH) to determine the incidence of translocation (12;21) and the poten tial usefulness of FISH as an adjunct to conventional cytogenetic analysis. With the use of specific chromosome paints, 4 of 31 patients with B-lineag e childhood ALL (13%) demonstrated rearrangements of chromosomes 12 and 21, and therefore, were considered to harbor the translocation, which had not previously been detected by conventional karyotyping. However, none of thes e positive cases revealed the standard reciprocal t(12;21)(p12;q22) as the sole abnormality involving chromosomes 12 and 21. The study confirms the fe asibility and advantages of introducing FISH screening for t(12;21) in pedi atric ALL cases and demonstrates the usefulness of FISH screening as a back up to concurrent cytogenetic analysis to resolve variant translocations and aberrant results. The presence of t(12;21) has also been correlated to cli nical data to assess the prognostic significance of this translocation on i ts own or in association with other prognostic features. (C) Elsevier Scien ce Inc., 1999. All rights reserved.