EWSR1 and rhabdomyosarcoma: Also, positivity for the break-points and fusion genesinvolving EWSR1 is typical only for this last tumor.12 A promisor HEY1-NCOA2 fusion genes were identified in mesenchymalchondrosarcoma and are absent in other chondrosarcoma subtypes.13 Rhabdomyosarcomas and lymphomas involving bone can be excluded by the absenceof their respective skeletal muscle and lymphoid biomarkers.12