Ewing sarcoma of the tibia mimicking fibrous dysplasia

Ewing Sarcoma of the Pelvis with an Atypical Radiographic Appearance: A Mimicker of Non-malignant Etiologies

Ewing sarcoma (ES) is a primary malignant bone tumor which most commonly arises in children and young adults. The common clinical presentation with ES includes nighttime pain or pain related to activity, though patients may also present with a combination of localized swelling, a palpable mass, pathologic fracture, and constitutional symptoms. Clinical diagnosis may be delayed when a patient presents with clinical or imaging findings that overlap with non-malignant etiologies, such as fibrous dysplasia (FD) or osteomyelitis. Furthermore, multimodality imaging, including computed tomography (CT), magnetic resonance imaging (MRI), and nuclear medicine may prove inconclusive in particular cases. Suspicion for malignancy should not be overlooked. A biopsy must be considered, unless the diagnosis is evident, such as a clinical response to antibiotics in the setting of osteomyelitis. 

Localized Ewing sarcoma of the tibia

Ewing sarcoma (ES) is a high-grade malignant primary round cell tumour of bone in which there is commonly extension into extraosseous soft tissues at the time of diagnosis. This report details the clinical, radiological and pathological features of a case of ES of the tibia in which there was extensive osseous involvement but no infiltration beyond the periosteum into surrounding soft tissue. We also record the findings of one other ES case that exhibited similar behaviour. Both cases were male, involved the tibia and had the characteristic t (11;22) (q24;q12) translocation. No recurrence of tumour or metastasis has been seen in these two cases, both of which have had 6 years follow-up. Our findings indicate that there is heterogeneity in the behaviour of ES and show that localized ES is associated with a good prognosis.