Intradural extramedullary hemangiopericytoma of the thoracic spine infiltrating a nerve root: A case report and literature review

Study Design.: Review the presentation and diagnosis of an intradural extramedullary hemangiopericytoma of the thoracic spine. Objective.: To present a rare case of intradural, subpial hemangiopericytoma in the thoracic spine, with a brief overview of the literature. Summary of Background Data.: Spinal intradural extramedullary hemangiopericytoma is rare entity that radiographically mimics nerve-sheath tumors. These lesions are typically diagnosed at surgery performed due to suspicion of tumor. Methods.: A 20-year-old man who presented with back pain, leg weakness, and sphincter incontinence. MR imaging demonstrated an intradural extramedullary lesion at the T9-T10 level that was isointense on T1- and T2-weighted images and homogeneously enhancing after administration of gadolinium, with cystic components seen on T2-weighted images. The preoperative diagnosis was meningioma or schwannoma. Results.: At surgery, the lesion was bluish and completely subpial, with apparent nerve root invasion. Pathological examination revealed a neoplasm adjacent to a nerve root with possible focal infiltration. Abundant reticulin fibers and widened, branching vascular channels imparting a staghorn appearance were seen. Up to five mitotic figures were counted in one high-power field. On immunostaining, the neoplastic cells were diffusely immunoreactive for CD99 and immunonegative for EMA, CD34, and S-100 protein. The pathological diagnosis was consistent with anaplastic hemangiopericytoma, WHO grade III. Conclusion.: This is the ninth report of spinal intradural hemangiopericytoma. The location of the neoplasm supports the hypothesis that hemangiopericytoma may arise from the spinal pial capillaries.