Clinical History: 7 year-old male presents with neck pain, diplopia and lethargy. Sagittal post-gadolinium T1-weighted (1A), axial post-gadolinium T1-weighted (1B), and axial T2-weighted (1C) images are provided. What are the findings? What is your diagnosis?
Findings
Figure 2: A large, multilobulated mass is centered within the clivus. It demonstrates heterogeneous enhancement (2A and 2B) with areas of low T1 signal resulting in a “honeycomb” appearance. The mass is very T2 hyperintense (2C). It extends posteriorly into the prepontine and premedullary cisterns down to the upper cervical central canal, exerting mass effect on the brainstem, cervicomedullary junction and upper cervical cord (red arrowheads). It extends anteriorly into the sphenoid sinus as well as into the nasopharynx and oropharynx (blue arrowheads).
Diagnosis
Chordoma
Introduction
Chordoma is a malignant neoplasm that arises from remnants of the primitive notochord. The notochord is a transient embryologic structure that plays an important role in embryogenesis of the vertebrate.1 Intraosseous remnants of this embryological structure can remain into adulthood, extending from the dorsum sella (Figure 3) to the tip of the coccyx (Figure 4). The majority of chordomas arise at either end of the notochord with 50% arising in the sacrococcygeal region, 35% arising at the skull base and 15% arising in the mobile spine.2
Epidemiological studies show a higher prevalence of chordoma in males.3 Chordomas are most common in adulthood, affecting people in their 5th to 6th decades. Less than 5% of cases occur before the age of 20, with most of these cases arising in the skull base.4,5
Chordomas, originating within the bone, lead to osseous destruction and frequently exhibit a disproportionately large soft tissue component. Imaging is crucial for identifying spinal cord chordomas and detailing their locoregional extent prior to surgical excision.
Figure 3: Sagittal T1-weighted (3A) and sagittal (3B) and coronal (3C) post-gadolinium T1-weighted images of a 73 year-old man who presented with diplopia reveal an expansile, enhancing lesion (arrows) arising from the basisphenoid that extends to the level of the sella superiorly and invades the sphenoid sinus anteriorly compatible with a chordoma. The lesion is hyperintense on the coronal T2-weighted image (arrows, 3D) and appears distinct from the pituitary gland. On CT, the lesion has expanded the sphenoid sinus anteriorly (arrowheads) on the axial images (3E) and demonstrates areas of osseous erosion (dotted arrows) on the coronal CT image (3F). Images courtesy of Dr. Franz J. Wippold, M.D.
Figure 4: A sagittal T1-weighted image (4A) through the sacrum of an 82-year old man who presented with buttock pain demonstrates a pathology-proven chordoma (arrows) arising from the coccyx that is hypointense to normal marrow on the T1-weighted images with a large soft tissue component. The lesion is very T2 hyperintense on the sagittal (4B) and axial (4C) T2-weighted fat-suppressed images and demonstrates avid contrast enhancement on the axial fat-suppressed T1-weighted post-contrast images (4D). Images courtesy of Dr. Matthew S. Parsons, M.D.
Clinical Presentation
Signs and symptoms at time of patient presentation vary depending on tumor location but are typically insidious in onset. Skull base chordomas most commonly present with headache and diplopia due to cranial nerve (CN) VI involvement in Dorello’s canal.6 Patients may also present with ophthalmoplegia due to involvement of CN III, CN IV and CN VI in the cavernous sinuses, visual loss due to compression of the optic nerves or chiasm, or facial pain due to compression of CN V. Lateral growth can compress CN VII or VIII in the cerebellopontine angles, leading to facial palsy or hearing loss and vertigo, respectively. Large chordomas may extend inferiorly to the jugular foramina, affecting CN IX through XII.
Sacral chordomas commonly present with pain, weakness or bowel and bladder dysfunction. Spinal chordomas typically present with pain, radicular symptoms or signs and symptoms of cord compression.
Radiologic Features
On imaging, chordomas should be strongly considered when a destructive osseous lesion is identified in the sacrococcygeal region or skull base that contains a large soft tissue component that is very T2 hyperintense to marrow (Figure 5). In the mobile spine, chordomas typically originate in the vertebral body, leading to osseous destruction and often present with a large paravertebral soft tissue mass.7
On CT, chordomas appear as destructive lytic lesions with a soft tissue mass that commonly contains irregular intratumoral calcifications (Figure 6). Tumors may contain areas of cystic degeneration or tumoral hemorrhage. On postcontrast CT, chordomas demonstrate variable enhancement.
Chordomas are best characterized by MRI. On T1-weighted images, tumors are typically T1 hypointense to marrow but may contain foci of T1 hyperintensity in the setting of tumoral hemorrhage. Marked T2 hyperintensity is a hallmark of these lesions on T2-weighted imaging due to the presence of vacuolated cellular components that contain fluid.8 Chordomas typically demonstrate heterogeneous enhancement with a honeycomb appearance corresponding to areas of hypoenhancement. Greater enhancement has been associated with worse outcomes (Figure 7).9
Because local recurrence (seeding) along the operative path may occur, postoperative imaging should encompass the surgical tract.10
Figure 5: Sagittal T1-weighted (5A), sagittal fat-suppressed T1-weighted post-contrast (5B), and sagittal (5C) and coronal (5D) fat-suppressed T2-weighted images through the sacrum in a 24 year-old man who presents with pelvic pain reveal a lesion arising from the coccyx with a large, multi-lobulated presacral soft tissue component (arrows). The lesion demonstrates areas of heterogeneous enhancement (arrowheads) and is very hyperintense on T2. An axial CT non-contrast CT image through the pelvis demonstrates the large pre-sacral soft tissue component (asterisks) of the lesion (5E). Images courtesy of Dr. Matthew S. Parsons M.D.
Figure 6: Axial (6A) and sagittal (6B) non-contrast CT images in soft tissue windows and sagittal CT image in bone windows demonstrates a large mass (arrows) arising within the lower sacrum and coccyx with osseous destruction (arrowheads). The mass contains a large pre-sacral soft tissue component that abuts and displaces the rectum and contains irregular intratumoral calcifications. Images courtesy of Dr. Franz J. Wippold, M.D.
Pathology and Grading
On gross pathology, chordomas are lobulated, gelatinous masses that are typically gray in color with areas of calcification and hemorrhage.2 There are four histological variants described: conventional chordomas, chondroid chordomas, dedifferentiated chordomas and anaplastic chordomas (poorly differentiated). Conventional chordomas contain multivacuolated “physaliphorous” cells admixed with epithelioid cells arranged in lobules, sheets and cords.11
Chondroid chordomas contain a component of hyaline cartilage matrix. Dedifferentiated chordoma is a biphasic tumor containing areas of classic chordoma alongside areas of high-grade spindle cell neoplasm. Anaplastic chordoma is an aggressive form of chordoma involving areas of conventional chordoma admixed with poorly differentiated elements. 11
Treatment and Prognosis
The overall median survival for chordoma is 7 years due to the local aggressive nature of these tumors and risk of recurrence. 11 Dedifferentiated and anaplastic variants have a worse prognosis. The chondroid chordoma variant portends a more favorable prognosis.12
En bloc surgical resection followed by adjuvant radiation therapy is the treatment of choice. Recurrent disease is common, most commonly occurring locally. Metastatic disease is seen in 7-14% of patients and includes metastases to lymph nodes, lung, bone and soft tissue.13
Differential Diagnosis
Ecchordosis Physaliphora
Ecchordosis physaliphora is a small (typically <1 cm) intradural, ectopic notochord remnant that is most commonly found along the dorsum of the clivus but can be found anywhere from the skull base to the sacrum.4 These lesions are asymptomatic and are typically discovered incidentally. Histopathologically, ecchordosis physaliphora consists of physaliphorous cells admixed with myxoid matrix without necrosis or mitoses.14
On MRI, ecchordosis physaliphora is hypointense to brain on T1-weighted imaging and isointense to CSF on T2-weighted imaging. As opposed to chordomas, these lesions do not enhance and remain stable in size on follow-up examinations. On CT, ecchordosis physaliphora results in a scalloped defect of the clivus. A small osseous stalk at the base of these lesions visualized on CT that connects the clival lesion to an intradural component is a pathognomonic finding (Figures 8 and 9).
Figure 8: Axial T2-weighted images (8A) through the brain demonstrates a T2 hyperintense, ovoid, intradural lesion (arrows) in the prepontine cistern that deviates the basilar artery flow-void (arrowhead) to the left compatible with ecchordosis physaliphora. On the axial T1-weighted (8B) and post-gadolinium T1-weighted images (8C), the lesion demonstrates thin peripheral enhancement (arrows). There is no associated diffusion restriction (asterisk) on the diffusion-weighted images (8D). An axial CT image in bone windows (8e) reveals an osseous stalk (arrowhead) at the base of the lesion which is pathognomonic for this entity. Images are courtesy of Dr. Franz J. Wippold, M.D.
Figure 9: A sagittal T2-weighted image through the cervical spine (9A) performed for neck pain revealed an incidental T2 hyperintense ovoid structure involving the dorsal clivus (arrow). Follow-up images through the brain confirm a T2-hyperintense lesion resulting in a defect in the dorsal clivus on the axial T2-weighted images (arrows) (9B). On the sagittal T1-weighted images (9C) the lesion is hypointense to marrow. The sagittal post-contrast, fat-suppressed T1-weighted images through the brain (9D) and axial post-contrast images (9E) demonstrate that the lesion is non-enhancing (arrowheads). The appearance, location and lack of enhancement are classic for ecchordosis physaliphora.
Benign Notochordal Cell Tumors
Benign notochordal cell tumors are benign, intraosseous lesions with notochordal differentation. These lesions may be detected radiologically and are often incidental findings. Autopsy data reveals benign notochordal cell tumors may be present in up to 12% of the population. 15
On CT, benign notochordal cell tumors may be occult or show minimal sclerosis without evidence of osseous erosion. Similar to chordomas, benign notochordal cell tumors are hypointense to marrow on the T1-weighted images and hyperintense on the T2-weighted images. These lesions do not typically enhance; enhancement is an atypical feature. Most importantly, benign notochordal cell tumors will not change on subsequent imaging studies (Figures 10 and 11).
Figure 10: Sagittal T1-weighted images (10A) through the lumbar spine reveal a T1 hypointense lesion within the S2 vertebral body (arrow). On sagittal STIR images (10B), the lesion is very hyperintense (arrow). Post-contrast T1-weighted, fat-suppressed image (10c) demonstrates faint contrast enhancement (asterisk). Although the appearance and location is good for chordoma, repeat images performed years later demonstrate no interval change. The S2 lesion is mildly sclerotic on sagittal (10D) and axial (10E) CT images (arrowheads) in bone windows. The lack of osseous destruction and stability of this lesion are most consistent with a benign notochord cell tumor. The presence of faint enhancement is an atypical feature.
Figure 11: Sagittal (11A) and axial (11B) fat-suppressed T2-weighted images through the sacrum from a 48 year-old woman with sacroiliac joint pain demonstrates a well-circumscribed T2 hyperintense lesion within the coccyx (arrows). Post-contrast T1-weighted fat-suppressed images (11C) reveal no corresponding enhancement (arrowhead). A subsequent follow-up MRI revealed stability of the lesion. The appearance and stability are most compatible with benign notochord cell tumor.
Chondrosarcoma
Chondrosarcomas are malignant cartilaginous tumors. Although most commonly found in the long bones and pelvis, they may also arise in the skull base and mobile spine. Similar to chordomas, chondrosarcomas cause osseous destruction on CT. Chondrosarcomas, however, typically display chondroid matrix mineralization with “ring and arc” calcifications. On MRI, both chondrosarcomas and chordomas are T1-hypointense to bone marrow and very T2-hyperintense. Chondrosarcomas typically demonstrate peripheral enhancement and enhancement of internal septae with non-enhancing portions corresponding to areas of hyaline cartilage or necrosis. Whereas chordomas are midline lesions, chondrosarcomas develop off-midline. In the skull base, chondrosarcomas classically arise from the petroclival synchondrosis as opposed to chordomas that arise from the midline clivus( Figure 12).
Figure 12: Sagittal STIR images (12A) performed on a 63 year-old male with neck pain and stiffness reveal an incompletely evaluated T2 hyperintense left-sided skull base lesion ultimately found to represent a chondrosarcoma (arrows). Subsequent MR images through the brain confirm the presence of a lesion arising near the left petroclival synchondrosis. Axial T1-weighted images (12B) through the skull base demonstrate an expansile lesion centered on the left petroclival synchondrosis that is hypointense to marrow (asterisk). Axial (12C) and coronal (12D) post-contrast T1-weighted images reveal avid homogenous enhancement with extension into the left cerebellopontine angle (arrowheads). Axial T2-weighted images through the brain (12E) and coronal fat-suppressed FLAIR images (12e) reveal the lesion is T2 hyperintense (blue arrows).
Giant Cell Tumor Sacrum
Giant cell tumors are locally aggressive neoplasms composed of osteoclastic giant cells. Giant cell tumors are the second most common primary sacral tumors following chordomas.16
Giant cell tumors are lytic lesions arising in bone without an associated matrix on CT. On MRI, giant cell tumors are typically T1 hypointense to marrow with intermediate to high signal on T2-weighted imaging. They demonstrate heterogeneous contrast enhancement (Figure 13).
Figure 13: MR images of the sacrum and coccyx were performed on a 39-year-old woman with coccydynia. Sagittal T1-weighted images (13A) reveal a large mass centered within the 5th sacral segment that also involves the coccyx with extension into the presacral soft tissues and into the lower sacral canal and sacral hiatus (arrows). The lesion is slightly hypointense to marrow on the T2-weighted images (13B) and demonstrates avid enhancement on the coronal fat-suppressed T1-weighted images (arrowheads, 13C). Pathology was consistent with giant cell tumor of the sacrum.
Plasmacytoma
Plasmacytoma is a solitary plasma cell tumor that may arise in bone or soft tissue. Plasmacytomas most commonly arise in the vertebral bodies. On CT, they are typically lytic, destructive lesions and may result in a pathologic compression fracture. Plasmacytomas are hypointense to marrow on the T1-weighted images with variable iso-to hyperintense signal on T2 and avid contrast enhancement. Plasmacytoma should be considered in the differential diagnosis for spinal osseous lesions in adults (Figure 14).
Figure 14: An ovoid T1-hypointense mass centered within the S2 vertebral body on sagittal T1-weighted images (14A) was discovered in an 88-year-old man with low back pain (arrows). Sagittal T2-weighted fat-suppressed images (14B) through the sacrum demonstrate a T2 hyperintense mass with extension into the sacral canal (arrows). The lesion enhanced on sagittal (14C) and axial (14D) post-contrast T1-weighted fat suppressed images (arrowheads). Pathology was consistent with plasmacytoma.
Metastatic Disease
Osseous metastases in the skull base, sacrum and mobile spine may mimic chordoma and should be included in the differential diagnosis when they cause osseous destruction and are T2-hyperintense to marrow (Figure 15). The presence of multiple lesions favors metastatic disease over chordoma.
Figure 15: Sagittal T1-weighted images (15A) through the lumbar spine performed on a 90-year-old with low back pain reveal a T1 hypointense, marrow replacing lesion centered within the S2 vertebral body with extension into S1 and S3 (arrows). The lesion is hyperintense to marrow on the sagittal T2-weighted (15B) and sagittal STIR images (15C) (arrows). Biopsy was performed which revealed metastatic lung cancer.
Sacral Tarlov Cysts
Tarlov cysts are type II meningeal cysts—extradural meningeal cysts containing neural tissue arising near the sacrum. They are CSF-filled expansions of the nerve root sheath. The morphology can vary from small simple cysts to large, complex, multicystic masses. When large, Tarlov cysts result in osseous remodeling with scalloping of the posterior sacral vertebral bodies. On MRI, the lesions follow the signal characteristics of CSF and do not enhance (Figure 16). Given their Sacral location and signal intensity, Tarlov cysts should be considered when encountering a T2-hyperintense mass in the region of the sacrum.
Figure 16: Sagittal T2-weighted images (16A) through the lumbar spine reveal a well-circumscribed T2 hyperintense, cystic appearing structure centered within the sacral canal that scallops the posterior margin of the sacral vertebral bodies (arrows). Precontrast sagittal T1-weighted images (16B) and postcontrast sagittal T1-weighted images (16C) confirm the lesion contains simple fluid without associated enhancement (asterisks). Axial T2-weighted (16D) and axial postcontrast T1-weighted images confirm a cystic appearing, nonenhancing lesion enlarging the sacral foramina and sacral canal (arrowheads) compatible with a large sacral Tarlov cyst.
Conclusion
Chordomas are locally aggressive, midline malignant neoplasms that arise from notochord remnants. Although they most commonly occur in the sacrum and skull base, they can arise anywhere along the extent of the notochord. The radiologist should consider the diagnosis of chordoma when encountering a T2 hyperintense, enhancing lesion with osseous destruction and a large soft-tissue component arising anywhere from the skull base to the sacrum.
References
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