Chapter 7 Intramedullary Tumors
Spinal cord intramedullary tumors are mostly benign. Primary intramedullary tumors originate from glial cell, neuronal cell, or other connective tissue cells. Glial tumors are astrocytoma, ependymoma, and oligodendroglioma. Astrocytomas are neoplasms of astrocytic origin within the spinal cord which demonstrate immunoreactivity for glial origin cells. They infiltrate into the surrounding spinal cord tissue, which makes radical resection difficult. Ependymomas, another glial tumor, are from the ependymal lining cells of the central canal in the spinal cord. They rarely show infiltrative growth pattern. Oligodendrogliomas are composed of proliferations of neoplastic oligodendroglial cells.
Intramedullary tumors from vascular tissue are hemangioblastomas and cavernous angiomas. Spinal cord hemangioblastomas are vascular neoplasms of benign nature that occur sporadically or in association with von Hippel–Lindau (VHL) disease. They are usually attached to the pial surface. Cavernous angiomas are composed of thin-walled, dilated, abnormal, vascular channels without neural tissue.
Tumors of neuronal components are gangliogliomas, neurocytomas, and embryonal neoplasms. Gangliogliomas are composed of both glial and neuronal neoplastic cells. The glial component is typically piloid to fibrillary, and a dysplastic neuronal portion also is identified.
Most spinal ependymomas are histologically benign and rarely show infiltrative growth. Though they do not form tumor capsules, the interface between the tumor mass and the surrounding normal cord tissue is relatively well defined.4
High-grade ependymomas demonstrate greater cellularity, a sheet-like growth pattern, increasing mitotic activity, nuclear anaplasia, and microvascular proliferation, as compared with grade II neoplasms. It may be difficult in some circumstances to distinguish high-grade ependymomas from grade IV astrocytomas.