Chordomas: A Roentgenologic Study of Sixteen Cases Previously Unreported

Abstract

Chordomas are neoplasms of relatively low malignancy which arise from remnants of the notochord. Almost all patients with chordomas require radiologic examination at some time during the course of the disease. Except for the lesions of the nasopharynx and sacrum, which may be detected by inspection and palpation, roentgenography affords the best opportunity to make the correct diagnosis prior to operation. It is the purpose of this paper to review, in summary, the records of 16 cases of histologically proved chordoma previously unreported in the literature and to discuss the roentgenologic abnormalities which help to differentiate these tumors from other neoplasms of the axial skeleton. Incidence Chordomas are rare tumors. For almost a century, from the time Luschka (11) described gelatinous excrescences projecting from the basisphenoid (1856) until 1944, a total of 252 chordomas were described in the literature. Reports of the tumor are to be found more commonly in recent literature than in the past. Chordomas may occur at any point in the axial skeleton, from within the skull to the coccyx. Of the 252 cases collected from the literature by Faust, Gilmore, and Mudgett (7), approximately 37 per cent were cranial, 13 per cent were vertebral, 48 per cent were sacrococcygeal, and the remaining few were eccentric. The tumors occur twice as frequently in men as in women. Mabrey (12) found that cranial chordomas appeared most frequently during the third and fourth decades of life, while the sacral tumors were seen more commonly during the fifth and sixth decades. The infrequent occurrence of these tumors in children is not well understood, especially in view of their relationship to tissues prominent during fetal life. Developmental and Pathologic Anatomy The notochord, which forms the primitive central skeleton of all vertebrates, extends as a cylindrical rod from the buccopharyngeal membrane to the coccyx. As the embryo develops, mesodermal tissue surrounds the notochord to form the vertebrae and intervertebral disks. The intravertebral portion disappears, except for rare chordal vestiges, while the intervertebral portion normally remains as the nucleus pulposus of the intervertebral disks. The cephalic portion of the notochord forms a sigmoid curve through the basal plate of the skull in the midsagittal plane so that, following regression, cell rests may be found along the dorsal surface of the clivus intracranially, within the clivus, or in the retropharyngeal tissues. Horwitz (9), from a study of fifty human embryos and fetuses, concluded that heterotopic chordal vestiges may undergo neoplastic metaplasia more readily than normal remnants, as the topographic distribution of the former corresponded closely to the sites of occurrence of chordomas. The ectopic vestiges of the notochord normally regress with advancing age. Schmorl (16) demonstrated chordal remnants in 9 adult cadavers in the dissection of over 3,000 human vertebral columns.