Article Sections

Introduction

Ewing sarcoma is an aggressive, bony malignancy most often diagnosed in adolescents.  It typically affects the long bone diaphyses ( Figure 1), pelvis, or axial skeleton.  X-ray classically demonstrates a central permeative ("moth-eaten") lesion with a layered ("onion skin") periosteal reaction.

Epidemiology

Ewing sarcoma is the second-most common primary bone malignancy in children (after osteosarcoma), with a peak incidence between ages 10-15.  It is rare among adults.

Pathogenesis

Ewing sarcoma is a primitive tumor of unclear origin (likely arising from neuroectodermal or mesenchymal stem cells).  Most cases are driven by a translocation involving EWSR1 on chromosome 22 and FLI1 on chromosome 11 (ie, a t(11;22) translocation).  This results in a fusion protein that functions as an abnormal transcription factor and leads to uncontrolled cell proliferation.

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