Abstract
RATIONALE: Extraosseous Ewing sarcoma (EES) is a rare manifestation within the Ewing sarcoma tumor family (ESFT). Its clinical manifestations lack specificity, intestinal obstruction is the main symptom but can also present with abdominal pain, gastrointestinal bleeding, and other discomforts, making it prone to misdiagnosis as intestinal mesenchymal tumor. PATIENT CONCERNS: A 29-year-old male was admitted to the hospital with intestinal obstruction symptoms and abdominal CT suggesting "left abdominal occupation." DIAGNOSIS: The patient was initially misdiagnosed as intestinal mesenchymal tumor, and was later definitively diagnosed as abdominal Ewing sarcoma by postoperative pathology and genetic testing. INTERVENTIONS: Due to the patient's surgical indication, surgical resection with exploratory laparotomy was performed and then the patient underwent systemic chemotherapy. OUTCOMES: Intraoperatively, we found a 15-cm tumor originating from the proximal jejunum, with invasion into the peritoneum, duodenum, jejunum, and colon. Finally, the pathological report revealed Ewing sarcoma. LESSONS: Giant abdominal Ewing sarcoma with a diameter of 15 cm is rare. Considering postoperative pathology and genetic testing, abdominal Ewing sarcoma was suspected. The patient was successfully treated using surgery.