ABSTRACT
M olecular analysis o f gene fusions expressed in human tumors is providing numerous insights into the oncogenic process. Most chimeric onco proteins characterized to date appear to act as aberrant transcription factors, likely func tioning in transformation by dysregulating the expression o f key target genes (reviewed in ref. 1). Among solid tumors, bone and soft tissue sarcomas o f childhood have been par ticularly fruitful for the identification of oncogenic gene fusions.1,2 Moreover, their characterization has revealed very consistent correlations between different gene fusion subtypes and the specific tumors that they are expressed in. Detection o f fusion transcripts in pathologic specimens has therefore become very useful as a diagnostic modality. This is particularly relevant for childhood sarcomas, which tend to be extremely primitive in ap pearance and therefore very difficult to differ entiate from each other morphologically.3 Since initial diagnosis often determines which treatment protocol a patient is entered on, accurate pathologic classification is a critical prognostic factor for these patients.
