Detection of prognostically relevant genetic abnormalities in childhood B-cell precursor acute lymphoblastic leukaemia: recommendations from the Biology and Diagnosis Committee of the International Berlin-Frankfürt-Münster study group.

Treatment of childhood acute lymphoblastic leukaemia (ALL) has improved considerably in recent years. A contributing factor has been the improved stratification for treatment according to a number of factors, including genetic determinants of outcome. Here we review the current diagnostic criteria of genetic abnormalities in precursor B-ALL (BCP-ALL), including the relevant technical approaches and the application of the most appropriate methods for the detection of each abnormality. The abnormalities with the most significant impact for treatment and management of BCP-ALL are t(9;22)(q34;q11)/BCR-ABL1, t(4;11)(q21;q23)/MLL-AFF1 and near-haploidy/low hypodiploidy for high risk stratification and, to a lesser extent, t(12;21)(p13;q22)/ETV6-RUNX1 and high hyperdiploidy for good risk management. Apart from the numerical abnormalities, these can be routinely tested for by reverse transcription polymerase chain reaction, providing a basic yet informative screen. However, cytogenetics, particularly fluorescence in situ hybridization may provide reliable alternative detection methods dependent upon the preferred technical approach within each protocol.