Clinical and Imaging Features of Primary Intradural Extramedullary Ewing Sarcoma.

Primary intradural extramedullary Ewing sarcoma (PIEES) is a very rare and aggressive tumor with poorly recognized radiological features. In this case series, we present our institutional experience with PIEES with emphasis on imaging and temporal evolution of the disease. In total, 8 patients with pathological diagnosis of PIEES were included in this study. All patients were symptomatic at time of presentation. MRI findings demonstrated T1 isointensity and T2 slightly hyperintensity relative to skeletal muscle, T2 hypointensity relative to CSF, and homogeneously enhancement in all cases with spinal cord edema/cord compression or cauda equina nerve roots compression. Tumor recurrence occurred in six patients (6/8, 75%). None of the patients developed recurrence outside the CNS. Four patients (50%) were deceased at the time of our study. In conclusion, PIEES is an extremely rare malignancy with poor outcomes. This case series highlights imaging features of PIEES and its temporal evolution including patterns of recurrence while reinforcing the importance of distinguishing PIEES from benign intradural lesions.ABBREVIATIONS: PIEES = Primary intradural extramedullary Ewing sarcoma, IQR = interquartile range, CI = confidence interval.