The t(11.22)(q24.q12) results in expression of a chimeric RNA product, EWS-FLI1. 
This RNA product is expressed in over 85% of tumours belonging to the Ewing's 
family, and is increasingly used as a definitive characteristic of these 
tumours. In this study, we evaluated reverse transcriptase-polymerase chain 
(RT-PCR) for EWS-FLI1 fusion transcripts in 18 neurally derived small round cell 
tumours. These included six Ewing's family tumours and 12 neuroblastomas. 
EWS-FLI1 fusion transcripts were identified in all six Ewing's tumours, but also 
in two of the 12 neuroblastomas. One neuroblastoma contained the classic type 1 
fusion transcript, and the second a type 1 transcript containing a 66 bp (base 
pair) insert that was not derived from the EWS or FLI1 gene. The presence of 
EWS-FLI1 fusion products in RNA extracted from primary neuroblastoma suggests 
the identification of EWS-FLI1 fusion transcripts is not pathognomonic for 
tumours of the Ewing's family. The clinical significance of these fusion 
transcripts in neuroblastoma is not known.