Renal Ewing Sarcoma Mimicking Neuroblastoma: A Multitracer PET/Scintigraphic Imaging Pitfall.

Renal Ewing sarcoma (EWS) is an exceptionally rare pediatric malignancy that may mimic neuroblastoma on conventional imaging. We report a 6-year-old boy presenting with a left suprarenal mass suspicious for neuroblastoma. The initial biopsy was inconclusive. I-131 metaiodobenzylguanidine (mIBG) scintigraphy demonstrated no tracer uptake within the mass. Subsequent Ga-68 DOTANOC PET/CT revealed only mild somatostatin receptor expression, whereas F-18 FDG PET/CT showed intense hypermetabolism. Given the discordant molecular imaging profile, repeat biopsy with fluorescence in situ hybridization confirmed EWSR1 gene rearrangement consistent with renal Ewing sarcoma. This case highlights the diagnostic value of multimodality nuclear imaging in pediatric renal masses and emphasizes that an mIBG-negative, intensely FDG-avid lesion with low somatostatin receptor expression should prompt consideration of renal EWS and re-evaluation of histopathology.