Tumours defined as Ewing sarcoma (ES) constitute a group of highly malignant 
neoplasms that most often affect children and young adults in the first 2 
decades of life. The EWS/Fli-1 fusion gene, a product of the translocation 
t(11;22) (q24; 12), is detected in 95% of ES patients. Recently, it was 
validated that cells emit a heterogeneous mixture of vesicular, organelle-like 
structures (microvesicles, MVs) into their surroundings including blood and body 
fluids, and that these MVs contain a selected set of tumor-related proteins and 
high levels of mRNAs and miRNAs. In this present study, we detected the Ewing 
sarcoma-specific EWS/Fli-1 mRNA in MVs from the culture medium of ES cell lines 
carrying t(11;22) (q24; 12). Also, we detected this fusion gene in approximately 
40% of the blood samples from mice inoculated with xenografts of TC135 or A673 
cells. These findings indicate the EWS/Fli-1 mRNA in MVs might be a new 
non-invasive diagnostic marker for specific cases of Ewing sarcoma.