RESUMO
Extraskeletal Ewing's sarcoma is a rare primary malignant soft tissue tumor that has the same pathological characteristics of skeletal Ewing's sarcoma. It is known that the differential diagnosis of Ewing's sarcoma from undifferentiated rhabdomyosarcoma, neuroblastoma, reticulum cell sarcoma, and malignant lymphoma by the histologic studies only are not easy because their histologic findings are nearly similar each other. Therefore, immunohistochemical method, electron microscopic examination, cytogenetic study, or molecular gene study are used together to confirm the diagnosis. It chiefly involves the lower extremity, soft tissues of the paravertebral region, and adjacent chest wall. We recently experienced a case of extraskeletal Ewing's sarcoma of duodenum in a 21-year old female. The patient underwent Whipple's operation and postoperative combined chemotherapy were done.