EWSR1-ETS fusion genes are genetic alterations commonly found in certain types of cancers, particularly in Ewing sarcoma and some primitive neuroectodermal tumors. These fusions occur when the EWSR1 gene on chromosome 22 combines with an ETS family gene, such as FLI1 or ERG, leading to the production of a hybrid protein that can disrupt normal cellular functions. The resulting fusion proteins often act as transcription factors, influencing the expression of various genes involved in cell growth and survival. This abnormal gene activity contributes to tumor development and progression, making EWSR1-ETS fusions important targets for research and potential therapies in oncology.