Surgical pathology of spinal schwannomas: A light and electron microscopicanalysis of tumor capsules

OBJECTIVE: Although spinal schwannomas are often encountered, the pathology of the tumor capsule has not been reported. In this study, we describe the ultrastructural pathology of the tumor capsule of spinal schwannomas. METHODS: In 18 patients who underwent total removal of spinal schwannomas ( C2-conus), the tumor capsule was collected and examined by light and electr on microscopy. RESULTS: The thickness of the tumor capsule ranged from 15 to 800 mum (most ly 30-100 mum) and was composed of three layers from the surface to the cen ter: 1) a thinly stretched nerve tissue layer; 2) a fibrous layer of fibroc ytes, abundant collagen fibers, and tumor vessels; and 3) a thin transition al layer intermingled with fibrous components and tumor cells. The thicknes s of each layer varied in different regions of the surface. There was no cl ear separation between the tumor capsule and the neoplastic tissue, even on the electron microscopic level. A number of nerve fibers ran through the f ibrous layer and beneath the capsule as well as in the nerve tissue layer. CONCLUSION: Compared with vestibular schwannomas, which have been reported to be covered by an extremely thin layer (3-5 mum) of connective tissue, sp inal schwannomas were well encapsulated. The capsule was composed of three distinct components; however, the cleavage between thin capsule and tumor c ells was indistinct, and the thickness of the axon-containing capsule varie d from site to site. Therefore, resection of the nerve of tumor origin, rat her than enucleation, would be justified to avoid tumor recurrence. Surgeon s should be aware of this pathology when performing the procedure.