Extraskeletal Ewing sarcoma (EES) is a rare tumor that primarily affects children and lacks specific clinical signs. Diagnosis is confirmed through imaging techniques, histology, and molecular diagnostics. Treatment typically involves surgical intervention and chemotherapy. We present the case of a 15-year-old female with a history of abnormal mass enlargement in the right flank area. An initial diagnosis of Wilms tumor was made, and the patient underwent a right open radical nephrectomy. However, the tumor recurred eight months after nephrectomy, necessitating a metastasectomy. Chemotherapy was started to immediately target the tumor recurrence. Next-generation sequencing done on the open radical nephrectomy and metastasectomy samples revealed the presence of the EWSR1-FLI1 fusion gene in both specimens, confirming the final diagnosis to be primary renal Ewing sarcoma. Despite undergoing a right open radical nephrectomy for the primary tumor site, a metastasectomy during tumor recurrence, and chemotherapy, the patient’s prognosis remained poor.

John Lorenz G. Mirhan completed his medical degree at St. Luke’s College of Medicine in Quezon City, Philippines. He is a chief resident at the Southern Philippines Medical Center, Department of Pathology and Laboratories located in Davao City Philippines. He is completing a 4-year training program in combined surgical and clinical pathology.