Epidemiology
It mainly affects children, adolescents, and young adults, and can start in bone or soft tissue. It can be mistaken for infection because of pain, fever, or inflammatory changes; biopsy and molecular studies are decisive.
Basic features
A small round cell tumor causing pain, occasional fever, and aggressive lesions in the pelvis, femur, tibia, or other bones. The diagnosis is confirmed by the characteristic EWSR1::FLI1 fusion (or, less often, EWSR1::ERG and other FET::ETS fusions), which separates it from the other genetically defined small round cell sarcomas.
Usual treatment
Systemic chemotherapy, followed by surgery, radiotherapy, or both, depending on the location and the response. Before chemotherapy starts it is worth discussing fertility preservation with the team, because some of these treatments can affect it and the options have to be raised beforehand.
Outcomes and prognosis
Ewing sarcoma is sensitive to chemotherapy, and the outlook depends above all on whether there are metastases at diagnosis, on the tumor's size and location, and on the response to the initial treatment. It is considerably better in localized disease; metastatic or recurrent disease calls for more intensive treatments and long-term follow-up.