Extra-osseous Ewing sarcoma (buttock)
Non-tender palpable right buttock lump. Hard and non-compressible. Otherwise well with no rash. No other lumps.
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The right buttock lump is barely visible on T1, hyperintense on T2 and enhances post-contrast with prominent rim-enhancement. These are not specific findings, but in the absence of history of infection or trauma, concerning for a soft-tissue sarcoma.
This small right buttock mass lesions was excised and confirmed histologically to be extra-osseous Ewing sarcoma.
Imaging findings are not specific, but a muscle lesion demonstrating T2 hyperintensity and post-contrast rim enhancement has a differential including abscess, haematoma and sarcoma and in the absence of infection or trauma, the latter becomes more likely. 60% of soft-tissue sarcomas in children are rhabdomyosarcomas, but in this case, histological assessment confirmed Ewing sarcoma.