Extraosseous Ewing Sarcoma in a Pelvic Region: A Case Report

Area of Science:

• Oncology
• Pediatric Oncology
• Skeletal and Soft Tissue Tumors

Background:

• Ewing sarcoma is the second most common pediatric bone malignancy.
• Extraskeletal Ewing sarcoma is rare, with primary pelvic origin being exceptionally uncommon.
• This case highlights a rare presentation of extraskeletal Ewing sarcoma in the pelvic region.

Observation:

• A 17-year-old female presented with a progressive lower abdominal mass and pain.
• CT revealed a large pelvic lesion (12.9 x 9.8 x 9.3 cm).
• Biopsy confirmed a small round blue cell tumor with specific immunohistochemical markers (CD99, vimentin, FLI-1) and high proliferation (Ki-67 40%).

Findings:

• The patient received neoadjuvant chemotherapy, surgical resection, and radiotherapy.
• Complete tumor resolution was achieved following the comprehensive treatment regimen.
• Immunohistochemistry confirmed the diagnosis of Ewing sarcoma.

Implications:

• This case underscores that EES can occur in diverse soft tissue locations, including the pelvis.
• Distinguishing EES from other soft tissue sarcomas is crucial for appropriate management.
• Multimodal therapy (chemotherapy, surgery, radiotherapy) can lead to favorable prognoses in EES.