A Case of Primary Renal Ewing Sarcoma With Metastatic Presentation and Review of Multimodal Management.

Primary Ewing sarcoma of the kidney (ESK) is an exceptionally rare and aggressive malignancy, representing less than 1% of renal tumors. It typically affects young adults and often presents at an advanced stage, leading to a poor prognosis. Diagnosis requires a multidisciplinary approach integrating histopathology, immunohistochemistry, and molecular analysis. A 29-year-old male patient presented with a one-and-a-half-year history of right flank pain and one year of painless, intermittent hematuria. Initial management at a local hospital for a suspected inflammatory lesion was unsuccessful. A contrast CT urogram revealed a large (19 cm), locally invasive right renal mass with aortocaval lymphadenopathy. Histopathological examination of a biopsy specimen revealed a malignant round cell tumor. Immunohistochemistry was positive for vimentin, NKX2.2, CD99, and synaptophysin, confirming the diagnosis of Ewing sarcoma. A staging PET-CT demonstrated metastatic disease involving the liver, inferior vena cava (with tumor thrombus), lymph nodes, and multiple skeletal sites. The patient received eight cycles of alternating VDC/IE (vincristine, doxorubicin, cyclophosphamide / ifosfamide, etoposide) chemotherapy, resulting in a significant reduction in the primary tumor and resolution of the IVC thrombus and skeletal metastases. He subsequently underwent cytoreductive nephrectomy. The final pathology confirmed a 7 cm Ewing sarcoma with negative margins and no lymph node involvement. Unfortunately, the patient did not receive adjuvant chemotherapy and expired four months post-surgery. ESK is a diagnostic and therapeutic challenge. This case underscores the utility of a multimodal approach, where neoadjuvant chemotherapy can effectively downstage even metastatic disease, facilitating surgical resection. However, the overall prognosis remains poor, particularly for metastatic presentations, highlighting the urgent need for more effective and less toxic therapeutic regimens.