J Neurosurg 75:980-984, 1991
Extraosseous spinal chordoma Case report FRANCIS H. TOMLINSON, M.B.,B.S., F.R.A.C.S., BERND W. SCHEITHAUER, M.D., GARY M. MILI.ER, M.D., AND BURTON M. ONOFR10, M.D. Departments of Neurosurgery, Laboratory Medicine and Pathology, and Diagnostic Radiology, Mayo Clinic, Rochester. Minnesota An extraosseous extradural tumor of the lumbar region with the histological appearance of chordoma produced symptoms in a 58-year-old woman. The tumor occupied the epidural space and produced scalloping of the adjacent vertebral body and pedicle without associated bone destruction. The location of the tumor within Batson's plexus and lack of osseous connection facilitated complete removal. Although the lesion exhibited the classic histological features of a chordoma, it differed significantly in its extraosseous location. Like the rare intradural chordoma arising in the cranium, this tumor presumably represents neoplastic development in an extraosseous notochordal rest. KEy WORDS
"
chordoma
9
bone tumor
HORDOMAS,tumors presumably derived from notochordal rests, are rare. Most are located in the sacrococcygeal and clival regions. Only 15 % of all chordomas arise within true vertebrae, more than one-half of these being encountered in the lumbar region. 18 Extraosseous processes that histologically resemble a chordoma include ecchordosis physaliphora 14'~7.22.25and intradural chordoma. ~'4'8"~3'~6'23The latter tumors are rare and are confined to the cranial region. The term "ecchordosis physaliphora" describes midline intracranial lesions of notochordal origin, arising in the region of the clivus and basilar artery. These small asymptomatic and largely intradural masses are considered hamartomas. Like intraosseous notochordal rests, they are developmental lesions but, in contrast, ecchordoses often exhibit a minor intraosseous and a dominant intradural component, the connection being a delicate pedicle traversing a dural defect. Intradural chordomas are extremely rare and, although they resemble classic chordomas in terms of both their notochordal origin and microscopic features, they are clinicopathologically distinct. Topographically, they resemble ecchordoses in that some demonstrate a delicate bone-associated pedicle; however, they differ in being larger and more cellular than ecchordoses. Furthermore, unlike other
C
980
ecchordosis physaliphora
9 ectopia
chordomas, intradural chordomas are amenable to resection. We report a case of a lumbar extraosseous extradural tumor with histological features of classic chordoma. The extradural tumor lay within the loose areolar tissue of Batson's plexus, demonstrated no osseous involvement, and was completely removed. Case Report
This previously healthy 58-year-old woman presented with a 2-month history of lumbar, right sacroiliac joint, and right thigh pain. The initial lumbar pain, which developed after a prolonged period of sitting, was severe for a number of hours then slowly moderated over 5 days without fully abating. During this time, she also developed right lateral thigh pain that did not respond to rest. Sitting, especially driving, aggravated the pain, whereas standing and lumbar hyperextension provided some relief. The patient was not aware of progressive neurological loss. Examination. Physical examination was unremarkable aside from a finding of tenderness over the right sacroiliac joint and a mildly diminished deep-tendon reflex at the fight knee. Laboratory investigations were within normal limits for the patient's age. Radiological J. Neurosurg. / Volume 75 /December, 1991
Extraosseous spinal chordoma
FIG. 2. Lt!jl: Postmyelography computerized tomography scan at the level of the L-3 neural foramen confirming a noncalcified extradural extraosseous mass. Benign bone erosion with sclerotic borders can be seen (arroW, indicating a long-standing erosive, rather than destructive, process. Right: Computerized tomography scan at the L-2 interspace demonstrating a focal disc herniation on the right (arro~,j. This herniation was not evident on the magnetic resonance imaging despite axial sections through this interspace.
FiG. l. Left parasagittal magnetic resonance image (TR 450 msec, TE 15 msec) showing expansion of the L-3 neural foramen by a low-intensity lesion (arrow), which erodes the L-3 pedicle and vertebral body.
investigations included magnetic resonance (MR) imaging with gadolinium enhancement of the lumbar region and an iopamidol myelogram with computerized tomography (CT) of the lower four lumbar vertebrae. Delayed CT of L-2, L-3, and L-4 at 6, 12, and 24 hours postmyelography demonstrated two abnormalities: 1) a disc protrusion at the level of the right L-2 space with inferior migration to the right L-3 pedicle, and 2) a 2cm nonenhancing mass that both filled and expanded the left L-3 neural foramen and produced scalloping of the posterior aspect of the left L-3 vertebral body (Figs. 1 and 2). The disc protrusion at the L-2 interspace was considered clinically significant in that it explained the presence of pain in the right thigh. Back pain was ascribed to both the extruded disc and the mass effect of the epidural lesion. Laminectomy and discectomy with exploration of the epidural process were recommended. Operation. Surgery was performed under general anesthesia by one of the authors (B.M.O.). The procedure included: a right partial hemilaminectomy and total facetectomy of L-2 with removal of the disc and ligament; a left partial hemilaminectomy and total facetectomy of L-3 with removal of the extradural tumor; and bilateral, posterolateral fusion of L2-4 with autogenous iliac bone grafting. The yellow-brown spherical tumor was situated between the scalloped pedicle of the L-3 vertebra and nerve root. It lay within the loose areolar tissue of Batson's plexus and did not involve surrounding structures such as the common dural sac, nerve roots, vertebral body, or pedicle or ligamentous J. Neurosurg. / Volume 75 / December, 1991
structures. The solid, spherical, circumscribed tumor wall was surrounded by delicate filamentous connective tissue and contained soft material that could be aspirated, as well as viscous fluid. The position of the tumor at L-3 and the friability of the tumor tissue resulted in piecemeal removal. Both of these factors raised the possibility of tumor recurrence and seeding. Histological, immunocytochemical, and ultrastructural studies confirmed the diagnosis of chordoma (Figs. 3 and 4). Postoperative Course. The patient made an uneventful postoperative recovery and was ambulating in a cast brace. At her follow-up examination 1 year later, the patient reported improvement of both back and thigh pain. The lumbar fusion was considered sound. Biannual MR imaging will be performed to identify tumor recurrence should it occur. Discussion
The interest of this case lies not only in the nature and location of the incidentally discovered tumor but also in its radiological presentation as an asymptomatic lesion at one lumbar level associated with a symptomatic disc extrusion at another lumbar level. Additionally, it represents an example of intraspinal extraosseous ehordoma, a lesion not previously described. Chordomas involving true vertebrae are uncommon and account for only 15% of all cases. ~ Of extravertebral tumors, 50% involve the sacrococcygeal region and 35% occur in the skull base, most often the clivus. 1~ Fully one-half of chordomas involving true vertebrae affect the lumbar region. Like their counterparts at other sites, such tumors are considered to arise from notochordal rests. Embryological Considerations A developmental lesion related to chordoma is the ecchordosis physaliphora. It is uncommon, occurs al981
F. H. Tomlinson, el al.
FIG. 3. Photomicrographs of the tumor specimen. L~j[i: A portion of the tumor with sheet-like growth of vacuolated cells. H & E, x 250. Cemer. A portion of the tumor with typical features of physaliphorous cells. H & E, • 100O. Ri,~,bt. A portion of the tumor showing strong uniform keratin reactivity. Immunostain, x 160.
most exclusively in the prepontine and clival regions, and is encountered in 0.5% to 5% of autopsy specimens. ~4,~7,2~_.~_5Ecchordoses consist of mucoid mulberryshaped nodules that lie largely in the intradural space but are attached via a delicate pedicle to the clivus, the connection being by way of a minute dural aperture. Histologically, they are identical to notochordal tissue? -~ The occurrence of prepontine ecchordosis is presumably related to development, since complex notochordal folding occurs in this region during embryogenesis.7 ~5,24 Notochordal rests in the true vertebrae are rare 2 and are primarily located centrally or posteriorly within vertebral bodies. 2 Additionally, studies of human fetal material have identified notochordal tissue eccentrically within the vertebral bodies -~ and also lying on their anterior and posterior surfaces. 1~ Such extraosseous rests were connected to the main notochordal mass. It appears, therefore, that notochordal tissues may literally be "squeezed out of the bodies" by the pressure of developing cartilage. It is postulated that rare "ectopic" chordomas might arise from such rests. A purported example with unusual light microscopic features was reported by Maesen, et aL; t2 however, their extraosseous tumor lacked "bubbly" cytoplasm, contained little stromal mucopolysaccharide, and exhibited both a high mitotic index and extensive necrosis. Although the term "ecchordosis physaliphora verte982
bralis" was coined by Ulich and Mirra -~1 to denote intraosseous notochordal rests or heterotopias, its use in this restricted sense is confusing. These loci were micro- rather than macroscopic, were entirely intraosseous, and bore no physical resemblance to ecchordosis physaliphora occurring in the cranial region. To be analogous to the intracranial ecchordosis, the designation should be expanded to include extraosseous lesions. In a recent article, Kurokawa, el al., "~ described what they considered to be an ecchordosis physaliphora within extradural tissues in the high cervical region. Their illustration demonstrates a chondroid tumor-like nodule that differs histologically from cranial ecchordosis. Radiographic Features
Although the histological, immunocytochemical, and ultrastructural features of this tumor are those of ordinary cranial, vertebral, or sacral chordoma, the tumor described in this report exhibits a different topography and growth pattern, being extraosseous and confined to the epidural space. Scalloping of the pedicle and body of the lumbar vertebrae is attributed to compression and remodeling rather than to destruction of bone. A CT study of axial chordomas by Krol, et al.,9 showed that chordomas of true vertebrae centered upon the vertebral body and that invasion of the pedicle, lamina, and spinal processes were secondary events. Such tuJ. Neurosurg. / Volume 75 / December, 1991
Extraosseous spinal chordoma
FIG. 4. Electromicrographs of the tumor specimen. A: Cells with cytoplasmic vacuoles and clear glycogen lakes (arrow~) are present. Note the interdigitation of' cell membranes. • 1135. B: Section showing cells with an abundance of intermediate filaments (F). Note the interdigilation and desmosomal junctions. x 9880.
mors often showed extraosseous extensions that were out of proportion to the degree of osseous involvement and were most often anterior and lateral but did involve the posterior spinal area. The radiological appearance of our tumor was not diagnosed either on plain radiography, CT, or MR imaging. In fact, the imaging findings were atypical for vertebral chordoma and more characteristic of either a neurogenic neoplasm, such as neurilemoma or neurofibroma, an arachnoid cyst, or diverticulum. Plain radiographs of the lumbar spine did not demonstrate a destructive lesion, either lytic or blastic (both of which are typical of chordomas). The only abnormality demonstrated on CT was scalloping of the posterior portion of the vertebral body and enlargement of the neural foramen, both frequently seen in neurogenic tumors. As in the case of chordoma of true vertebrae, our patient's lesion did not show peripheral amorphous calcification, a common feature of sacral lesions. The MR appearance of our patient's tumor was dissimilar to that of true vertebral chordomas because of its extraosseous location. The signal changes seen were nonspecific, and the tumor did not enhance with gadolinium, which is unusual for a neoplasm. Increased T2weighted MR signal relative to cerebrospinal fluid, J. Neurosurg. / Volume 75 / December. 1991
which was present, has been described in some spinal and cranial chordomas with high mucoid content. 2~ The enhancement characteristics of chordomas on MR images have not been reported. Our experience suggests that at least some cranial chordomas enhance (unpublished data). The purported cervical ecchordosis of Kurokawa, et al.,~~ however, showed some similarities on MR imaging to our lesions: theirs was located within the epidural space and was associated with scalloping of the posterior surface of the vertebral body. The MR images showed a low-intensity mass. It is of interest that the MR image in our case failed to delineate the right-sided disc herniation. Surgical Implications The tumor in our patient lent itself to complete surgical removal. This is in sharp distinction to chordomas of the vertebral bodies, which are virtually unresectable. In a series of spinal chordomas reported by Sundaresan, et al., ~s 12 patients were diagnosed as having tumors of the true vertebrae; complete intralesional excision was achieved in one patient by "piecemeal removal within its capsule by curettage." In contrast to vertebral body chordomas, those of the sacrum may be amenable to en bloc resection. 983
F. H. Tomlinson, el al. Conclusions Based on our morphological and immunohistochemical studies, we propose that the tumor presented in this report, a bona fide intraspinal extraosseous extradural chordoma, had its origin in an ectopic notochordal remnant. The histogenetic relationship of this lesion to "ecchordosis physaliphora vertebralis'" is unclear. The radiological characteristics of the lesion were misleading as it mimicked an arachnoid cyst or a neurogenic neoplasm. Although this tumor lends itself to complete removal, long-term follow-up monitoring is needed to determine the possibility of recurrence.
12. 13.
14. 15.
16.
Acknowledgment The authors thank Ms. Mary Soper for assistance in preparation of this manuscript. References 1. Bartolini G: 11 cordoma del clivus quale causa di emorragia cerebrale: discussione anatomo-clinica su di una osservazione autopica. Boll Soc Ital Biol Sper 5D: 912-918, 1974 2. Beadle OA: The Intervertebral Discs. Observations on Their Normal and Morbid Anatomy in Relation to Certain Spinal Deformities. London: His Majesty's Statione~' Office, Medical Research Council Special Reports, 1931, No 161, pp 26-27 3. Cappell DF: Chordoma of the vertebral column with three new cases, d Pathol Bacteriol 31:797-814, 1928 4. Dahlin DC, MacCarty CS: Chordoma. A study of fiftynine cases. Cancer 5:1170-I 178, 1952 5. Ho KL: Ecchordosis physaliphoria and chordoma: a comparative ultrastructural study. Clin Neuropathol 4:77-86, 1985 6. Horten BC, Montague SR: Human ecchordosis physaliphora and chick emb~'onic notochord. A comparative electron microscopic study. Virchows Arch Pathol Anal 371:295-303, 1976 7. Horwitz T: Chordal ectopia and its possible relation to chordoma. Arch Pathol 31:354-362, 1941 8. Klebs E: Ein Fall yon Ecchondrosis spheno-occipitalis amylacea. Arch Pathol Anal Physiol Kiln Med 31: 396-399, 1864 9. Krol G, Sundaresan N, Deck M: Computed tomography of axial chordomas. J Comput Assist Tomogr 7: 286-289, 1983 10. Kurokawa H. Miura S, Goto T: Ecchordosis physaliphora arising from the cervical vertebra, the CT and MRI appearance. Neuroradiology 30:81-83, 1988 11. Linck A, Warstat D: Zur Kenntnis der malignen Chordome in der Sacro-Coccygealregion, zugleich ein Beitrag
984
17. 18. 19.
20. 21. 22. 23. 24. 25. 26.
zur Frage der Genese und Lokalisation maligner Chordome/iberhaupt. Beitr Kiln Chir 127:612-626, 1922 Maesen F. Baur C, Lamers J, et al: Chordoma of the thorax. Eur J Respir Dis 68:68-72, 1986 Mapstone TB, Kaufman B, Ratcheson RA: Intradural chordoma without bone involvement: nuclear magnetic resonance (NMR) appearance. Case report, d Neurosurg 59:535-537. 1983 Ribbcrt H: Ueber die Ecchondrosis physalifora sphenooccipitalis. Zentralbl AIIg Pathol 5:457-461, t 894 Sassin JF: lntracranial chordoma, in Vinken PJ, Bruyn GW (eds): Handbook of Clinical Neurology. Vol 18: Tumours of the Brain and Skull, Part IIl. Amsterdam: North-Holland, 1975, pp 151-164 Stare FC, Kamphorst W: Ecchordosis physaliphora as a cause of fatal pontine hemorrhage. Eur Neurol 21: 90-93, 1982 Stewart MJ, Burrow JLF: Ecchordosis physaliphora spheno-occipitalis. J Neurol Psychopathol 4:218-220, 1923 Sundaresan N, Huvos AG, Krol G, et ah Surgical treatment of spinal chordomas. Arch Surg 122:1479-1482, 1987 Sundaresan N, Krol G, Hughes JEO: Primary malignant tumors of the spine, in Youmans JR (ed): Neurological Surgery, ed 3. Philadelphia: WB Saunders, 1990, Vol 3, pp 3548-3573 Sze G, Uichanco LS IIL Brant-Zawadzki MN, et al: Chordomas: MR imaging. Radiology 166:187-191, 1988 Ulich TR, Mirra JM: Ecchordosis physaliphora vertebralis. Clin Orthop 163:282-289, 1982 Willis RA: Pathology of Tumours, ed 4. New York: Appleton-Centu~'-Crafts, 1967, pp 937-938 Wolfe JT III, Scheithauer BW: "lntradural chordoma" or "giant ecchordosis physalifora?" Report of two cases. Clin Neuropathol 6:98-103, 1987 Wright D: Nasopha~ngeal and cervical chordoma - some aspects of their development and treatment, d Laryngol Otol 81:1337-1355, 1967 Wyatt RB, Schochet SS Jr, McCormick WF: Ecchordosis physaliphora. An electron microscopic study, d Neurosurg 34:672-677, 1971 Yuh WT, Flickinger FW, Barloon TJ, et al: MR imaging of unusual chordomas, d Comput Assist Tomogr 12: 30-35, 1988
Manuscript received January, 8, 1991. Accepted in final form May 29, 1991. This work was supported in part by the James S. McDonnell Neurosurgical Fellowship of the Royal Brisbane Hospital Foundation to Dr. Yomlinson. Address reprint requests to: Bernd W. Scheithauer, M.D., Department of Laborato~ Medicine and Pathology, Mayo Clinic, Rochester, Minnesota 55905.
J. Neurosurg. / Ii~)lurne 75/December, 1991
Extraosseous spinal chordoma Case report FRANCIS H. TOMLINSON, M.B.,B.S., F.R.A.C.S., BERND W. SCHEITHAUER, M.D., GARY M. MILI.ER, M.D., AND BURTON M. ONOFR10, M.D. Departments of Neurosurgery, Laboratory Medicine and Pathology, and Diagnostic Radiology, Mayo Clinic, Rochester. Minnesota An extraosseous extradural tumor of the lumbar region with the histological appearance of chordoma produced symptoms in a 58-year-old woman. The tumor occupied the epidural space and produced scalloping of the adjacent vertebral body and pedicle without associated bone destruction. The location of the tumor within Batson's plexus and lack of osseous connection facilitated complete removal. Although the lesion exhibited the classic histological features of a chordoma, it differed significantly in its extraosseous location. Like the rare intradural chordoma arising in the cranium, this tumor presumably represents neoplastic development in an extraosseous notochordal rest. KEy WORDS
"
chordoma
9
bone tumor
HORDOMAS,tumors presumably derived from notochordal rests, are rare. Most are located in the sacrococcygeal and clival regions. Only 15 % of all chordomas arise within true vertebrae, more than one-half of these being encountered in the lumbar region. 18 Extraosseous processes that histologically resemble a chordoma include ecchordosis physaliphora 14'~7.22.25and intradural chordoma. ~'4'8"~3'~6'23The latter tumors are rare and are confined to the cranial region. The term "ecchordosis physaliphora" describes midline intracranial lesions of notochordal origin, arising in the region of the clivus and basilar artery. These small asymptomatic and largely intradural masses are considered hamartomas. Like intraosseous notochordal rests, they are developmental lesions but, in contrast, ecchordoses often exhibit a minor intraosseous and a dominant intradural component, the connection being a delicate pedicle traversing a dural defect. Intradural chordomas are extremely rare and, although they resemble classic chordomas in terms of both their notochordal origin and microscopic features, they are clinicopathologically distinct. Topographically, they resemble ecchordoses in that some demonstrate a delicate bone-associated pedicle; however, they differ in being larger and more cellular than ecchordoses. Furthermore, unlike other
C
980
ecchordosis physaliphora
9 ectopia
chordomas, intradural chordomas are amenable to resection. We report a case of a lumbar extraosseous extradural tumor with histological features of classic chordoma. The extradural tumor lay within the loose areolar tissue of Batson's plexus, demonstrated no osseous involvement, and was completely removed. Case Report
This previously healthy 58-year-old woman presented with a 2-month history of lumbar, right sacroiliac joint, and right thigh pain. The initial lumbar pain, which developed after a prolonged period of sitting, was severe for a number of hours then slowly moderated over 5 days without fully abating. During this time, she also developed right lateral thigh pain that did not respond to rest. Sitting, especially driving, aggravated the pain, whereas standing and lumbar hyperextension provided some relief. The patient was not aware of progressive neurological loss. Examination. Physical examination was unremarkable aside from a finding of tenderness over the right sacroiliac joint and a mildly diminished deep-tendon reflex at the fight knee. Laboratory investigations were within normal limits for the patient's age. Radiological J. Neurosurg. / Volume 75 /December, 1991
Extraosseous spinal chordoma
FIG. 2. Lt!jl: Postmyelography computerized tomography scan at the level of the L-3 neural foramen confirming a noncalcified extradural extraosseous mass. Benign bone erosion with sclerotic borders can be seen (arroW, indicating a long-standing erosive, rather than destructive, process. Right: Computerized tomography scan at the L-2 interspace demonstrating a focal disc herniation on the right (arro~,j. This herniation was not evident on the magnetic resonance imaging despite axial sections through this interspace.
FiG. l. Left parasagittal magnetic resonance image (TR 450 msec, TE 15 msec) showing expansion of the L-3 neural foramen by a low-intensity lesion (arrow), which erodes the L-3 pedicle and vertebral body.
investigations included magnetic resonance (MR) imaging with gadolinium enhancement of the lumbar region and an iopamidol myelogram with computerized tomography (CT) of the lower four lumbar vertebrae. Delayed CT of L-2, L-3, and L-4 at 6, 12, and 24 hours postmyelography demonstrated two abnormalities: 1) a disc protrusion at the level of the right L-2 space with inferior migration to the right L-3 pedicle, and 2) a 2cm nonenhancing mass that both filled and expanded the left L-3 neural foramen and produced scalloping of the posterior aspect of the left L-3 vertebral body (Figs. 1 and 2). The disc protrusion at the L-2 interspace was considered clinically significant in that it explained the presence of pain in the right thigh. Back pain was ascribed to both the extruded disc and the mass effect of the epidural lesion. Laminectomy and discectomy with exploration of the epidural process were recommended. Operation. Surgery was performed under general anesthesia by one of the authors (B.M.O.). The procedure included: a right partial hemilaminectomy and total facetectomy of L-2 with removal of the disc and ligament; a left partial hemilaminectomy and total facetectomy of L-3 with removal of the extradural tumor; and bilateral, posterolateral fusion of L2-4 with autogenous iliac bone grafting. The yellow-brown spherical tumor was situated between the scalloped pedicle of the L-3 vertebra and nerve root. It lay within the loose areolar tissue of Batson's plexus and did not involve surrounding structures such as the common dural sac, nerve roots, vertebral body, or pedicle or ligamentous J. Neurosurg. / Volume 75 / December, 1991
structures. The solid, spherical, circumscribed tumor wall was surrounded by delicate filamentous connective tissue and contained soft material that could be aspirated, as well as viscous fluid. The position of the tumor at L-3 and the friability of the tumor tissue resulted in piecemeal removal. Both of these factors raised the possibility of tumor recurrence and seeding. Histological, immunocytochemical, and ultrastructural studies confirmed the diagnosis of chordoma (Figs. 3 and 4). Postoperative Course. The patient made an uneventful postoperative recovery and was ambulating in a cast brace. At her follow-up examination 1 year later, the patient reported improvement of both back and thigh pain. The lumbar fusion was considered sound. Biannual MR imaging will be performed to identify tumor recurrence should it occur. Discussion
The interest of this case lies not only in the nature and location of the incidentally discovered tumor but also in its radiological presentation as an asymptomatic lesion at one lumbar level associated with a symptomatic disc extrusion at another lumbar level. Additionally, it represents an example of intraspinal extraosseous ehordoma, a lesion not previously described. Chordomas involving true vertebrae are uncommon and account for only 15% of all cases. ~ Of extravertebral tumors, 50% involve the sacrococcygeal region and 35% occur in the skull base, most often the clivus. 1~ Fully one-half of chordomas involving true vertebrae affect the lumbar region. Like their counterparts at other sites, such tumors are considered to arise from notochordal rests. Embryological Considerations A developmental lesion related to chordoma is the ecchordosis physaliphora. It is uncommon, occurs al981
F. H. Tomlinson, el al.
FIG. 3. Photomicrographs of the tumor specimen. L~j[i: A portion of the tumor with sheet-like growth of vacuolated cells. H & E, x 250. Cemer. A portion of the tumor with typical features of physaliphorous cells. H & E, • 100O. Ri,~,bt. A portion of the tumor showing strong uniform keratin reactivity. Immunostain, x 160.
most exclusively in the prepontine and clival regions, and is encountered in 0.5% to 5% of autopsy specimens. ~4,~7,2~_.~_5Ecchordoses consist of mucoid mulberryshaped nodules that lie largely in the intradural space but are attached via a delicate pedicle to the clivus, the connection being by way of a minute dural aperture. Histologically, they are identical to notochordal tissue? -~ The occurrence of prepontine ecchordosis is presumably related to development, since complex notochordal folding occurs in this region during embryogenesis.7 ~5,24 Notochordal rests in the true vertebrae are rare 2 and are primarily located centrally or posteriorly within vertebral bodies. 2 Additionally, studies of human fetal material have identified notochordal tissue eccentrically within the vertebral bodies -~ and also lying on their anterior and posterior surfaces. 1~ Such extraosseous rests were connected to the main notochordal mass. It appears, therefore, that notochordal tissues may literally be "squeezed out of the bodies" by the pressure of developing cartilage. It is postulated that rare "ectopic" chordomas might arise from such rests. A purported example with unusual light microscopic features was reported by Maesen, et aL; t2 however, their extraosseous tumor lacked "bubbly" cytoplasm, contained little stromal mucopolysaccharide, and exhibited both a high mitotic index and extensive necrosis. Although the term "ecchordosis physaliphora verte982
bralis" was coined by Ulich and Mirra -~1 to denote intraosseous notochordal rests or heterotopias, its use in this restricted sense is confusing. These loci were micro- rather than macroscopic, were entirely intraosseous, and bore no physical resemblance to ecchordosis physaliphora occurring in the cranial region. To be analogous to the intracranial ecchordosis, the designation should be expanded to include extraosseous lesions. In a recent article, Kurokawa, el al., "~ described what they considered to be an ecchordosis physaliphora within extradural tissues in the high cervical region. Their illustration demonstrates a chondroid tumor-like nodule that differs histologically from cranial ecchordosis. Radiographic Features
Although the histological, immunocytochemical, and ultrastructural features of this tumor are those of ordinary cranial, vertebral, or sacral chordoma, the tumor described in this report exhibits a different topography and growth pattern, being extraosseous and confined to the epidural space. Scalloping of the pedicle and body of the lumbar vertebrae is attributed to compression and remodeling rather than to destruction of bone. A CT study of axial chordomas by Krol, et al.,9 showed that chordomas of true vertebrae centered upon the vertebral body and that invasion of the pedicle, lamina, and spinal processes were secondary events. Such tuJ. Neurosurg. / Volume 75 / December, 1991
Extraosseous spinal chordoma
FIG. 4. Electromicrographs of the tumor specimen. A: Cells with cytoplasmic vacuoles and clear glycogen lakes (arrow~) are present. Note the interdigitation of' cell membranes. • 1135. B: Section showing cells with an abundance of intermediate filaments (F). Note the interdigilation and desmosomal junctions. x 9880.
mors often showed extraosseous extensions that were out of proportion to the degree of osseous involvement and were most often anterior and lateral but did involve the posterior spinal area. The radiological appearance of our tumor was not diagnosed either on plain radiography, CT, or MR imaging. In fact, the imaging findings were atypical for vertebral chordoma and more characteristic of either a neurogenic neoplasm, such as neurilemoma or neurofibroma, an arachnoid cyst, or diverticulum. Plain radiographs of the lumbar spine did not demonstrate a destructive lesion, either lytic or blastic (both of which are typical of chordomas). The only abnormality demonstrated on CT was scalloping of the posterior portion of the vertebral body and enlargement of the neural foramen, both frequently seen in neurogenic tumors. As in the case of chordoma of true vertebrae, our patient's lesion did not show peripheral amorphous calcification, a common feature of sacral lesions. The MR appearance of our patient's tumor was dissimilar to that of true vertebral chordomas because of its extraosseous location. The signal changes seen were nonspecific, and the tumor did not enhance with gadolinium, which is unusual for a neoplasm. Increased T2weighted MR signal relative to cerebrospinal fluid, J. Neurosurg. / Volume 75 / December. 1991
which was present, has been described in some spinal and cranial chordomas with high mucoid content. 2~ The enhancement characteristics of chordomas on MR images have not been reported. Our experience suggests that at least some cranial chordomas enhance (unpublished data). The purported cervical ecchordosis of Kurokawa, et al.,~~ however, showed some similarities on MR imaging to our lesions: theirs was located within the epidural space and was associated with scalloping of the posterior surface of the vertebral body. The MR images showed a low-intensity mass. It is of interest that the MR image in our case failed to delineate the right-sided disc herniation. Surgical Implications The tumor in our patient lent itself to complete surgical removal. This is in sharp distinction to chordomas of the vertebral bodies, which are virtually unresectable. In a series of spinal chordomas reported by Sundaresan, et al., ~s 12 patients were diagnosed as having tumors of the true vertebrae; complete intralesional excision was achieved in one patient by "piecemeal removal within its capsule by curettage." In contrast to vertebral body chordomas, those of the sacrum may be amenable to en bloc resection. 983
F. H. Tomlinson, el al. Conclusions Based on our morphological and immunohistochemical studies, we propose that the tumor presented in this report, a bona fide intraspinal extraosseous extradural chordoma, had its origin in an ectopic notochordal remnant. The histogenetic relationship of this lesion to "ecchordosis physaliphora vertebralis'" is unclear. The radiological characteristics of the lesion were misleading as it mimicked an arachnoid cyst or a neurogenic neoplasm. Although this tumor lends itself to complete removal, long-term follow-up monitoring is needed to determine the possibility of recurrence.
12. 13.
14. 15.
16.
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Manuscript received January, 8, 1991. Accepted in final form May 29, 1991. This work was supported in part by the James S. McDonnell Neurosurgical Fellowship of the Royal Brisbane Hospital Foundation to Dr. Yomlinson. Address reprint requests to: Bernd W. Scheithauer, M.D., Department of Laborato~ Medicine and Pathology, Mayo Clinic, Rochester, Minnesota 55905.
J. Neurosurg. / Ii~)lurne 75/December, 1991
