Imaging Findings of Extraosseous Chordomas Arising from the Cervical Spinal Region A Neuroradiologic Review R J McDonald MD PhD, C Inwards MD, J M Morris MD ASNR 2015 Chicago, IL

Outline 1. Embryologic Overview 2. Anatomic Overview 3. Pathologic Overview 4. Imaging Features of Extraosseous Chordomas 5. Differential Diagnosis 6. Biopsy Considerations 7. Conclusions

Embryologic Overview Notochord development Notochord arises from mesoderm spanning the length of the embryo Ectoderm forms a groove parallel to the notochord dorsally Neural tube forms from groove which gives rise to spinal cord and brain Notochord remnants in adult humans spans the primitive axis (red dashed line) and normally gives rise to the nucleus pulposus of the intervertebral discs. Chordomas can arise anywhere along the primitive notochord tract.

Anatomic Overview Spheno-Occipital (35%) Spine (15%) Most commonly arises from clivus Sites of Chordoma Occurrences Spine (15%) Least common location Sacro-Coccygeal (50%) Most common primary malignant sacral tumor

Pathologic Overview Cytokeratin AE1/AE3 40x H&E 40x 100x S-100 40x Brachyury 40x H&E Stain: Bubbly appearance (vacuoles) of cords and lobules of physaliferous cells separated by fibrous septa and myxoid stroma Immunohistochemistry: Positive for the structural protein cytokeratin (+++), calcium binding protein S-100 (++), and the conserved transcription factor brachyury (+) responsible for defining the midline of all bilaterian organisms

Case 1: 12 F w/ biopsy proven chordoma at C1-C2 T1 : Hypo to isointense T2 : Markedly hyperintense Gad : Hetero enhancement Imaging Pearls Lobulated/septated on T2 Markedly T2 hyperintense Anterior to vertebral artery Hypoattenuating to soft tissue Erosive bony remodeling * CT : Erosive remodeling (Aggressive) CT : Hypodense

Case 2: 47 M w/ biopsy proven chordoma at C5 T1 : Hypo to Isointense T2 : Markedly hyperintense (Encasing vertebral artery) Gad : Peripheral enhancement Imaging Pearls Can encase vertebral artery * Can invade central canal * Peripheral enhancement * Peripheral calcification * Permeative bone destruction * * Denotes imaging variant CT : Hypodense CT : Permeative changes *

Case 3: 43 F w/ biopsy proven chordoma at C4 * T1 : Hypo to Isointense T2 : Heterogenously hyperintense (Usually markedly hyperintense) Gad : Avid heterogenous enhancement Imaging Pearls Heterogenous T2 signal * Mixed osseous and extraosseous origin * Homogenous enhancement * Erosive bone destruction * Denotes imaging variant CT : Mixed osseous & extraossous origin CT : Erosive changes

Case 4: 52 M w/ recurrent chordoma at C2-C3 interspace s/p resection T1 : Hypo to Isointense T2 : Recurrence vs Postop Changes? Gad : Recurrence vs Postop Changes? * Imaging Pearls Incomplete resection  100% chance of slow regrowth. In the postoperative spine, T2 hyperintensity and enhancement from postoperative change can confound diagnosis of recurrent chordoma. Collect both axial and sagittal planes to confirm recurrence. SAG T2 : RECURRENCE!

Imaging Overview T1 Uniformly iso to hypointense relative to soft tissues T2 Uniformly hyperintense & lobulated/septated appearance Heterogenous appearance is a less common variant Gad Uniformly heterogeneous appearance is most common Peripheral enhancement is a less common pattern CT Erosive and/or permeative patterns of bone destruction Other The extent of osseous involvement can vary CT and MRI are complementary exams for chordomas

Differential Diagnosis Schwannoma – Most common/likely extraosseous extradural spinal lesion. When approaching a case, one should ask “why is this not a schwannoma?” Chondrosarcoma – Rare but can be extraosseous and mimic chordoma Chordoma – Rare (in the spine) and are a mimic of schwannoma Lymphoma – Appearance can vary but can mimic schwannoma and chordoma Meningioma – Extradural component can mimic schwannoma and chrodoma

Schwannoma vs Chordoma Imaging Discriminators Benign bone remodeling Chordoma is erosive/destructive Behind vertebral artery Chordoma is anterior to or encases it Dumbell-shaped exiting foramen. Chordoma erodes bone Can have overlap in T2 and Gad signal/appearance between Schwannoma and Chordoma. Schwannoma T2 : Hyperintense and heterogenous Gad : Avid peripheral Chordoma T2 : Hyperintense and homogenous Gad : Heterogeneous

* Chondrosarcoma vs Chordoma Imaging Discriminators T2 appearance can be similar to chordoma if there is a significant extraosseous component “Rings and arcs” with expanded matrix on CT can help discriminate CT complements MRI in these cases. Chondrosarcoma T2 : Hyperintense with septation CT : Arcs and rings * Chordoma T2 : Hyperintense with septation CT : Erosive Destruction

Lymphoma vs Chordoma Imaging Discriminators Lymphoma Chordoma T1 : hypo to isointense T2 : hypo to isointense Gad : homogenous CT : minimal erosion CT : adenopathy Chordoma T1 : hypo to isointense T2 : hyperintense Gad : varies CT : more erosion Imaging Discriminators Little to no bony destruction with lymphoma (vs moderate to extensive with chordoma). T2 hypo to isointense (vs hyperintense) & lacks cystic/lobulated appearance of chordoma. Homogenous enhancement with lymphoma (chordoma varies but is not as homogenous). Look for secondary signs of lymphoma on CT (e.g. bulky adenopathy) absent with a chordoma.

Meningioma vs Chordoma Imaging Discriminators T1 signal intensity is similar between meningioma and chordoma T2 signal of meningioma is typically less hyperintense Gad enhancement of meningioma is more homogenous than chordoma Look for dural tail of meningioma Meningioma T1 : hypo to isointense T2 : iso to mildly hyperintense Gad : homogenous Chordoma T1 : hypo to isointense T2 : hyperintense Gad : varies

Biopsy Options Biopsy Considerations Chordomas are slow-growing tumors with a marked propensity for recurrence when residual tissue remains Percutaneous biopsy will cause seeding of biopsy tract For this reason, chordomas are resected en bloc and biopsy tracts are also resected Choose approach carefully to minimize damage to other facial/neck structures due to required resection.

Conclusions Chordomas are benign slow-growing tumors that uncommonly arise from notochord remnants in the spine Imaging characteristics of chordomas are somewhat nonspecific and can be mistaken for schwannoma, meningioma, or lymphoma. Although rare, chordoma should remain on the differential of any extradural spinal mass. CT and MRI are complementary methods to help discriminate between these tumors – both should be used when possible. Due to the propensity for recurrence, particularly along biopsy tracts, and non-specific imaging characteristics, proper biopsy planning is crucial to minimize the risk of seeding/recurrence in the face/neck.