Extraskeletal Ewing sarcoma rarely involves the retroperitoneum. In a review of 24 EESs,3the authors found only 2 patients presenting with EES involving the retroperitoneum; in both cases, patients received only a palliative treatment with chemotherapy, with a follow-up of only 4 and 5 months, respectively. The most effective treatment is surgery combined with chemotherapy and high-dose radiation therapy.4When resectable, the surgical excision must be wide in accordance with the classic oncologic principles, and radiation therapy should be used as an adjuvant to resection in an attempt to improve local control, whereas chemotherapy should be considered preoperatively, in an attempt to shrink the tumor, and postoperatively, in an attempt to address the obscure systemic disease. Overall and disease-free survival have improved significantly in recent years, obtaining important results (77% and 55%, respectively) when multimodal therapy is used.5Retroperitoneal EES is a rare tumor but should always be considered in the differential diagnosis of any patient, of any age, with a soft tissue mass of the retroperitoneum. Even patients presenting with extensive involvement may benefit from an aggressive multimodal management strategy involving surgery, chemotherapy, and radiation therapy.