Extraosseous Ewing’s Sarcoma: Pictorial Review of Imaging Findings, Differential Diagnosis, and Pathologic Correlation

Abstract

Extraosseous Ewing’s sarcoma (EES), first described in 1969, is a malignant mesenchymal tumor just like its intraosseous counterpart. Although Ewing’s sarcomas are common bone tumors in young children, EESs are rarer and more commonly found in older children/adults, often carrying a poorer prognosis. We discuss the multimodality imaging features of EES and the differential diagnosis of an aggressive appearing mass in proximity to skeletal structures, with pathologic correlates. This review highlights the need to recognize the variability of radiologic findings in EES such as the presence of hemorrhage, rich vascularity, and cystic or necrotic regions and its imaging similarity to other neoplasms that are closely related pathologically.

Extraskeletal Ewing sarcoma of the sciatic nerve

“…Although most Ewing sarcomas arise from bone, up to 30% arise in soft tissue resulting in EES [10] . EES is a rare variant that affects older children and young adults with a worse prognosis [ 4 , 18 ]. These tumors most commonly occur in the upper thigh and gluteal region as well as the upper extremities and paravertebral region [ 4 , 14 , [18] , [19] , [20] ].…”

“…EES is a rare variant that affects older children and young adults with a worse prognosis [ 4 , 18 ]. These tumors most commonly occur in the upper thigh and gluteal region as well as the upper extremities and paravertebral region [ 4 , 14 , [18] , [19] , [20] ]. Less than 15 cases have described EES originating from peripheral nerves, with the first reported in 1918 [ 3 , 8 , 21 ].…”

“…In 85% of EES, a reciprocal translocation between chromosomes 11 and 22 is present, specifically t (11; 22) (q24; q12) resulting in the EWSR1-FLI1 gene [ 7 , 14 , [27] , [28] , [29] ]. About 10% of cases possess a translocation of t (21;22) (q22; q12) to produce the EWSR1-ERG gene [ 4 , [30] , [31] , [32] ]. Both of these chimeric genes encode proteins that induce aberrant oncogenic factors [ 14 , 19 , 32 ].…”

“…Ewing sarcoma family of tumors (EFT) is a spectrum of neoplastic disease that includes skeletal Ewing sarcoma, extraskeletal Ewing sarcoma (EES), primitive neuroectodermal tumor (PNET), Askin tumor (Ewing sarcoma of the thoracopulmonary region), and rarely visceral tumors [ 1 , 2 ]. EFT are malignant round cell tumors of mesenchymal origin that overall have a predilection for males under 30 years [ 3 , 4 ]. EES is an uncommon Ewing variant that poses diagnostic and therapeutic challenges due to its rarity and nonspecific radiologic findings.…”

Primary EWS/PNET of the lung with TP53 germline and SKT11 somatic mutation: A case report and review of the literature

“…Ewing's sarcoma is a rare and highly invasive mesenchymal tumor which belongs to the neuroectodermal tumor family, and includes Ewing's osteosarcoma, extra-skeletal Ewing's sarcoma, primitive neuroectodermal tumor (PNET), Askin tumor and atypical Ewing's sarcoma. 1,2 It accounts for 6%-8% of primary bone tumors in children and young adults, and its incidence peaks at 20, mostly in males. 3 Extra-skeletal EWS/PNET is clinically rare with very low incidence, which accounts for about 1% of soft tissue sarcoma.…”