PTGS2 and Ewing sarcoma: Whereas the expression of cyclooxygenase-2 (COX-2), an inducible enzyme active in inflammatory sites, has a tumour promoting activity in several adult cancers, studies in paediatric osteosarcoma, Ewing sarcoma, and rhabdomyosarcoma have failed to show any correlation between the activity of COX-2 and patient outcome [5].