Role of gene expression profiling for diagnosing acute leukemias.

Cytomorphology and cytochemistry in combination with multiparameter immunophenotyping today are the standard methods for establishing the diagnosis of acute leukemias. In addition, cytogenetics, fluorescence in situ hybridization, and polymerase chain reaction based assays provide important information regarding biologically defined and prognostically relevant subgroups and allow a comprehensive diagnosis of well defined subentities. With regard to the clinical setting a better understanding of the clinical course of distinct biologically defined disease subtypes is needed to select disease-specific therapeutic approaches. Paralleling the increase in knowledge on deregulated pathways in leukemia the development of new therapeutics is accelerated and therefore requires a detailed and comprehensive diagnostic tool. Revealing and quantifying the expression status of many ten thousands of genes in a single analysis the microarray technology holds this potential to become an essential tool for the molecular classification of leukemias. It may therefore be used as a routine method for diagnostic purposes in the near future. Furthermore, it is anticipated that new biologically defined and clinically relevant subtypes of leukemia will be identified based on gene expression profiling. This method may therefore guide therapeutic decisions.