Spinal and spinal cord tumors are primarily divided into three main categories based on the tissues from which they originate: Those originating from the spinal cord tissue itself, i.e., nerve cells, are called intramedullary tumors and are generally divided into two main groups: astrocytoma and ependymoma. Tumors originating from the membranes surrounding the spinal cord (dura mater, arachnoid) and other connective tissues are referred to as intradural-extramedullary; while those originating from the spinal bone structure or other tissues outside the spinal canal are extradural tumors.