Primary Renal Ewing Sarcoma in a Child: Diagnostic Reliance on Immunohistochemistry in a Resource-Limited Setting

Primary renal Ewing sarcoma (ES) is an extremely rare and aggressive malignancy, with fewer than 100 cases reported worldwide. Diagnosis is difficult because its clinical and radiologic features mimic more common renal tumors, particularly in children, and the challenge increases in resource-limited settings where molecular testing may not be available. We report a 12-year-old Palestinian boy presenting with flank pain, weight loss, and night sweats. Contrast-enhanced CT revealed a large left renal mass, and radical nephrectomy was performed. Histopathology demonstrated small round blue cells with strong CD99 and NKX2.2 expression and negative WT1 staining, supporting the diagnosis of primary renal Ewing sarcoma. Confirmatory EWSR1 rearrangement testing was unavailable. The patient-initiated adjuvant chemotherapy and showed no radiologic recurrence at 3 months. This case highlights the important diagnostic role of immunohistochemistry when molecular testing is limited.