When Common Tumours Hide in Uncommon Places: Paediatric Sacral Ewing Sarcoma With Metastases.

Ewing's sarcoma is a highly aggressive malignant small round blue cell tumour that typically affects the long bones and axial skeleton in children and adolescents. Sacral involvement is uncommon, often leading to diagnostic delays due to nonspecific symptoms. We report a case of a nine-year-old girl presenting with chronic back pain and weight loss, eventually found to have a large sacral mass with hepatic metastases. Imaging revealed a destructive presacral tumour with soft tissue extension, and histopathology confirmed Ewing's sarcoma with EWSR1 rearrangement. This case highlights the diagnostic challenges of rare anatomical sites, emphasises the value of multimodality imaging, and reinforces the importance of including Ewing's sarcoma in the differential for persistent paediatric back pain.