Extraspinal ependymomas. Report of three cases.

Spinal ependymomas may rarely arise from heterotopic ependymal cell clusters and thus occur in an extraspinal location. Presentation of three cases and a review of the literature reveal that these tumors have characteristic radiographic and clinical features. They occur mainly in patients in the third decade of life, and present either in the soft tissue posterior to the sacrum or in the pelvis. In the case of posterior tumors, the patient exhibits a mass which is usually mistaken for a pilonidal cyst. Patients whose tumor is pelvic in location present with sphincter disturbances or dysfunction of the sacral nerve roots. Conventional and computerized tomographic studies will reveal erosion of the sacrum. Myelography will demonstrate an extradural mass indenting the thecal sac from below. The protein in the cerebrospinal fluid will be normal. A combined posterior and anterior approach with the goal of complete tumor removal is the procedure of choice. If this is not feasible, then radiation therapy should be employed. Because of the increased incidence of systemic metastases, the average postoperative survival is approximately 10 years.