Limited remodelling of expansile Ewing sarcoma after treatment

Radiological findings of Ewing sarcoma have been well documented, and bone expansion or cystic change is known to be a relatively uncommon finding. On the other hand, expected changes in Ewing sarcoma after treatment have also been reported, e.g. regression of extraosseous soft tissue mass, regression and organization of the periosteal reaction, and remodelling of the lytic or sclerotic bone changes. However, remodelling of bone is often limited or incomplete. We saw an atypical change in Ewing sarcoma after treatment due to lack of significant remodelling of the expanding bone. Because such changes might be a cause of misdiagnosis, knowledge of it will help the radiologist in the follow up evaluation.