FISH at Diagnosis of Childhood Acute Lymphoblastic Leukemia

Overview

Classical cytogenetic analysis plays an important role in the diagnosis, classificat ion, therapy monitoring andprognosis of patients with leukemia. Many recurrent cytogenetic abnormalities with major prognostic values havebeen described in childhood ALL. Hyperdiploidy and/or t(12;21) are associated with good prognosis, whereas t(9;22)and/or rearrangements of MLL gene correlate with poor outcome and therefore early detection of these abnormalitiesis very important. FISH can overcome some limitations of conventional cytogenetic and molecular-genetic analysesand due to high sensitivity specific chromosomal aberrations in mitoses and/or interphase nuclei can be detected. Inthe Center of Oncocytogenetics of the 3rd Medical Department for assesment of hyperdiploidy and structuralrearrangements we use double-color FISH with centromeric and/or locus-specific probes and complex aberrationsare ascertained by whole chromosome painting probes and multicolor FISH. Among 275 children with ALL examinedduring the last 8 years by different FISH methods we found seven patients with translocation t(9;22) and 14 patientswith MLL rearrangements in bone marrow cells. Since 1988 we focus on detection of hyperdiploidy and/or t(12;21).High hyperdiploidy was found in 35 children, 10 of them had further complex rearrangements. Translocation t(12;21)was proved in 37 patients and complex rearrangements were found in 22 of them. FISH, cytogenetic andmolecular-genetic analyses become obligatory for the first diagnostic examination as well as for monitoring oftreatment effect in children with ALL.

Key words:
childhood ALL, FISH, conventional cytogenetics, molecular-genetic methods, mFISH.