The Ewing sarcoma family of tumors includes osseous Ewing sarcoma, extraskeletal 
Ewing sarcoma, primitive neuroectodermal tumor, and Askin tumor. They share a 
karyotype abnormality with translocation involving chromosomes 11 and 22. 
Histologically, these lesions demonstrate crowded sheets of small round blue 
cells. Imaging features of osseous Ewing sarcoma often suggest the diagnosis, 
with aggressive long-bone destruction in the metadiaphysis of an adolescent or 
young adult and an associated soft-tissue mass. Focal areas of cortical 
destruction are frequent, allowing continuity between the intraosseous and 
extraosseous components. This continuity is also commonly seen as subtle 
channels extending through the cortex at computed tomography or magnetic 
resonance (MR) imaging, a finding that reflects the underlying pathologic 
appearance. Extraskeletal Ewing sarcoma commonly demonstrates a nonspecific 
radiologic appearance of a large soft-tissue mass affecting the paraspinal 
region or lower extremity. Askin tumor represents extraskeletal Ewing sarcoma 
involving the chest wall. Imaging typically reveals a large pleural-based mass 
and associated pleural effusion. Treatment of these tumors is usually a 
combination of neoadjuvant chemotherapy followed by surgical resection, which 
may be supplemented with radiation therapy. Imaging, particularly MR, is also 
vital to evaluate response to neoadjuvant therapy, direct surgical resection, 
and detect local recurrence or metastatic disease.