Abstract
Ewing's sarcoma (EWS) of the kidney is an extremely rare and aggressive malignancy, accounting for less than 1% of renal tumors. This report presents a 42-year-old male who initially presented with hematuria and intermittent fever, with imaging studies suggesting a renal cell carcinoma (RCC). However, histopathological and immunohistochemical analysis, including CD99 positivity and NKX2.2 nuclear expression, confirmed the diagnosis of primary renal EWS. The patient was promptly started on neoadjuvant chemotherapy (VAC + IE [vincristine, adriamycin, cyclophosphamide, ifosfamide, and etoposide]), which he tolerated well without significant adverse effects. Given its nonspecific clinical and (18) F-fluorodeoxyglucose positron emission tomography/computed tomography scan presentation, the case highlights the diagnostic challenges in distinguishing renal EWS from more common renal neoplasms such as RCC. Early diagnosis through histopathology and immunohistochemistry is crucial for guiding appropriate management. Given the aggressive nature of renal EWS, a multimodal treatment approach involving chemotherapy followed by radical nephrectomy is essential for improving prognosis. This case sheds light on the importance of considering renal EWS in the differential diagnosis of renal masses and emphasizes the role of early intervention in enhancing survival outcomes.