Primary intra-axial Ewing sarcoma of the central nervous system: report of a rare case with literature review

Background Primary intra-axial Ewing sarcoma (EWS) is extremely rare and a highly aggressive small blue round cell tumor in the central nervous system (CNS). We reported a case of primary intra-axial CNS-EWS in a 30-year-old male and presented an extensive literature review of CNS-EWS cases. Case presentation A 30-year-old male had been diagnosed with a grade 2 astrocytoma in the left frontal lobe a year ago and had received chemotherapy and radiotherapy. He presented with a right-sided mass, which was revealed to be a 6 cm contrast-enhancing lesion with heterogeneous hemorrhagic areas in the right frontal lobe. The patient underwent emergent craniotomy for surgical excision. Histologically, the tumor was composed of high-grade, small, blue, round cells forming trabecular islands and rosettes which were separated by fibrovascular tissues. In immunohistochemical (IHC) examination, the tumor cells were positive for CD99 and FLI-1. Fluorescence in situ hybridization analysis revealed the presence of EWSR1 gene rearrangement. The histopathological, IHC, and molecular findings were consistent with a diagnosis of EWS. Further imaging did not show evidence of another primary site. The patient was followed up without further therapy and succumbed to the disease three months after the diagnosis. Conclusion EWS is very rare but an aggressive neoplasm in the CNS. Chemoradiotherapy may promote secondary cancers but it is unclear whether the development of EWS was associated with chemoradiotherapy that our case had received for astrocytoma. EWS should be considered when diagnosing a CNS tumor that shows small, blue, round cell tumor morphology. A combination of IHC and molecular tests is required for accurate diagnosis to ensure that all patients receive the most appropriate treatment to optimize outcomes. Keywords: Ewing sarcoma, Central nervous system, intra-axial, EWSR1