Intracranial Ewing sarcoma with whole genome study

Introduction Ewing sarcoma (ES) as a primary intracranial tumor is very rare. Recently, CNS embryonal tumors with ES-like genomic change have been reported. Patients and methods We report a case of intracranial Ewing sarcoma in a 13-year-old girl who complained of headache and migraine. The tumor had developed in the right middle cranial fossa with a mass effect on the brain with impending transuncal herniation. Results Undifferentiated small round cell morphology with completely negative results for friend leukemia integration 1 transcription factor (Fli-1) and a nonspecific cytoplasmic CD99-positive staining pattern mislead the diagnosis as central nervous system (CNS) embryonal tumor, NOS. However, whole genome sequencing (WGS) revealed Ewing sarcoma ( EWS )- Fli - 1 gene fusion, which was confirmed by fluorescence in situ hybridization study and the diagnosis was revised to ES. Conclusions This case is a true intracranial but extra-axial ES confirmed by WGS. We report this case of intracranial ES to demonstrate the importance of marker gene studies using FISH or NGS.