In a study of 514 surgically treated cases of intraspinal tumor, 29 patients had an initial diagnosis of protruded intervertebral disk. Of these 29 patients, 10 gave a history of trauma with which they associated the onset of their symptoms. Only 4 presented with the major complaint of night pain. The most common type of tumor simulating a protruded intervertebral disk was the extramedullary intradural neurofibroma (11 of 29) and the most common location was the lumbar region, but it was found that thoracic intraspinal tumors could simulate protruded lumbar intervertebral disks.