Primary Intracranial Ewing Sarcoma Invading the Superior Sagittal Sinus with EWSR1-FLI1 Gene Fusion and EWSR1 Gene Mutation: A Case Report and Literature Review

-BACKGROUND: Primary intracranial Ewing sarcoma (ES) is an extremely rare intracranial malignant tumor, mostly occurring in children and adolescents. Because of its rarity, the magnetic resonance imaging (MRI) features and treatment strategies of primary intracranial ES are still unclear.METHODS: The purpose of this study was therefore to report a case of pri-mary intracranial ES, whose molecular features included both EWSR1-FLI1 (EWS RNA binding protein 1-Friend leukemia integration 1) gene fusion and EWSR1 gene mutation. It is worth noting that this is the first reported case of ES invading the superior sagittal sinus and mostly causing occlusion. At the same time, there were polymorphisms of four drug metabolism-related enzymes in the tumor. Subsequently, we conducted a literature review to characterize the clinical features, imaging findings, pathological features, treatments, and prognoses of primary intracranial ESs.RESULTS: A 21-year-old female was admitted to the hospital with headache with nausea and vomiting for 2 weeks. An MRI showed a 3.8 3 4.0 cm large heterogeneous mass in the bilateral parietal lobe with peritumoral edema. The tumor invaded the superior sagittal sinus and mostly caused occlusion of the middle segment of the superior sagittal sinus. The mass was successfully removed using a neuromicroscope. Postoperative pathology indicated a primary intracranial ES. High throughput sequencing (next generation sequencing) showed that there was EWSR1-FLI1 gene fusion and EWSR1 gene mutation in the tumor, with polymorphisms of four drug metabolism-related enzymes and low tumor mutational burden. Subsequently, the patient received intensity modulated radiation therapy. The patient has signed an informed consent form.CONCLUSIONS: The diagnosis of primary intracranial ES depended on his-topathology, immunohistochemistry staining, and genetic testing. At present, total tumor resection combined with radiotherapy and chemotherapy is the most effective treatment. We report the first case of primary intracranial ES invading the superior sagittal sinus and causing middle segment occlusion, accompanied by EWSR1-FLI1 gene fusion and EWSR1 gene mutation.