Intradural extramedullary Ewing tumor of the lumbar spine

A 38-year-old man presented with a highly symptomatic lumbar intradural extramedullary tumor. MRI features strongly suggested a myxopapillary ependymoma, with a possible drop metastasis. No filum terminale or spinal-cord attachment to the tumor was seen intraoperatively. Histopathology, surprisingly, indicated a malignant round-cell tumor, strongly CD 99-positive, and FISH indicated a rearranged ESWR1 locus. A diagnosis of Ewing tumor (ET) was made. Only eight cases in the lumbar region have been previously reported.