Ewing sarcoma: A pictorial review of typical and atypical locations with reference to the updated 2020 WHO classification system

Summary Ewing sarcoma (ES) is a small round cell sarcoma which usually occurs in the paediatric and young adult age groups. This pictorial review briefly discusses and presents the typical skeletal and extraskeletal locations which ES is encountered, including the metadiaphysis of long bones, pelvis, chest wall and paravertebral regions. Five cases of ES in atypical locations are then presented along with an observation of demographic differences between skeletal and extraskeletal ES. These cases include ES arising from the metatarsal, scapula, breast, intracranial soft tissue and the paranasal sinuses. Presenting symptoms, treatment approach and prognosis are highly variable depending on the location; and multimodal imaging is centrepiece in the management process. Management usually includes any combination of chemotherapy, radiotherapy and surgery. The WHO classification system was updated in 2020 to include some of the rare genetic subtypes of ES. One such case of the BCOR subtype is demonstrated in this review and occurs in an atypical location. Whether these subtypes have distinct radiological features or a propensity to occur in atypical locations is an area for further research.