EXTRAOSSEOUS EWING’S SARCOMA OF THE PELVIC REGION IN THE PEDIATRIC POPULATION – A CASE REPORT

Abstract

Introduction: Primary extraosseous Ewing sarcoma is a rare malignant soft tissue tumor, accounting for a small proportion of the Ewing sarcoma family. Pelvic localization in the pediatric population is exceptionally uncommon. Treatment requires a multimodal approach including chemotherapy, surgery, and radiotherapy when indicated, while prognosis depends on patient age, tumor size, and the possibility of complete resection.

Case outline: We present the case of a 13-year-old boy admitted with acute urinary retention, accompanied by impaired urination, constipation, and lumbar pain lasting one month. Ultrasound and MRI revealed a large solid–cystic pelvic mass associated with bilateral grade II hydronephrosis. Tumor biopsy followed by histopathological, immunohistochemical, and FISH analyses confirmed the diagnosis of extraosseous Ewing sarcoma, with diffuse FLI-1 and NKX2.2 positivity.

Treatment was initiated according to the Euro-Ewing 2012 protocol. After six VIDE chemotherapy cycles, a significant reduction in tumor size was achieved. Therapy was continued with the VAI protocol with the aim of further tumor reduction and potential surgical resection. However, despite the initial favorable response, rapid disease progression occurred, leading to abandonment of surgical treatment and initiation of radiotherapy. Due to aggressive local tumor growth, infiltration of surrounding structures, and distant metastatic dissemination, a fatal outcome ensued.

Conclusion: Extraosseous Ewing sarcoma of the pelvic region is an extremely rare and aggressive malignancy in children. Definitive diagnosis relies on histopathological and immunohistochemical evaluation. Although multimodal treatment is essential, pelvic localization is associated with limited therapeutic options and an unfavorable prognosis.