Which EWSR1 gene fusion accounts for 80% of Ewing sarcoma cases?

The EWSR1 gene fusion that accounts for approximately 80% of Ewing sarcoma cases is the fusion between EWSR1 and the FLI-1 gene. This specific fusion results in the production of a chimeric transcription factor that plays a critical role in the pathogenesis of Ewing sarcoma by driving oncogenesis through the dysregulation of target genes.

EWSR1, which stands for Ewing Sarcoma Breakpoint Region 1, is involved in several gene fusion events in Ewing sarcoma, but the EWSR1-FLI1 fusion is the most prevalent and is considered a hallmark of the disease. The presence of this particular fusion is often utilized in diagnostic testing to confirm the diagnosis of Ewing sarcoma, alongside other clinical and histological features.

In contrast, other gene fusions involving EWSR1, such as with ERG, ETV1, and FEV, are less common and do not represent the majority of cases. While they may be relevant in specific contexts, they do not account for the overwhelming majority of Ewing sarcoma cases as the EWSR1-FLI1 fusion does. Hence, recognizing the significance of the EWSR1-FLI1