*Viewers will gain a visual understanding of the multi-modality imaging appearances and findings of extraosseous Ewing sarcomas in various anatomical sites. *Additionally, viewerswill be able to understand and recognize pathological correlates of extraosseous Ewing sarcomas. *Finally, viewers will be able to include extraosseous Ewing sarcoma in the differential diagnosis along with other soft tissue masses.

Ewing sarcoma was first described in 1921 by James Ewing as an osteolytic bone tumor composed of malignant, small round cells. Extraosseous Ewing sarcoma was first described in 1969; it is a rare, malignant mesenchymal tumor similar to its intraosseous counterpart. Although Ewing sarcomas areone of the most common bone tumors in children, extraosseous Ewing sarcoma is more commonly found in adults, and often carry a poorer prognosis [1]. This tumor has increasingly been reported from diverse...

The imaging findings of extraosseous Ewing sarcomas are variable in appearance and location, with a common theme. The imaging appearance is typically aggressive and complex. The lesions are large, solid, and heterogeneous, with some having cystic changes. Familiarity with the imaging appearance on various modalities is critical. Generally, these tumors are commonly seen in the deep soft tissues of the extremities, with lower extremities having a higher propensity than upper extremities,...

Extraosseous Ewing sarcoma should be considered when a circumscribed, solid, aggressive appearing mass is encountered in an older child/adolescent in the extremities or in close proximity to the skeletal structures. Familiarity of the radiologist with its radiological appearance is essential in providing an accurate differential diagnosis. Features including flow voids, T1 signal similar to muscle, proximity to bone, cystic changes/necrosis and lack of calcification all help consider...

1. Kim SW et al: Primary intradural extraosseous Ewing's sarcoma. J Korean Neurosurg Soc. 2009;45:179–181. 2. Weiss SW et al: Ewing's sarcoma/PNET tumor family and related lesions. In Weiss SW et al: Enzinger and Weiss' Soft Tissue Tumors. 5th ed. Philadelphia: Elsevier. 963-79, 2008. 3. Kransdorf MJ et al: Neurogenic tumors. In Kransdorf MJ et al: Imaging of Soft Tissue Tumors. 2nd ed. Philadelphia: Lippincott Williams & Wilkins. 371-4, 2006. 4.Christie DR et al: Diagnostic difficulties in...