Approximately 50 % of the cases in sacrococcygeal bones; nearly 20–40 % in skull base, most commonly in the clivus; and nearly 10–30 % in mobile spine, mainly in the body of cervical and lumbar vertebrae.
In pediatric patients, frequently in the base of the skull and the cervical spine.
Rare examples of extra-axial chordoma in bone or soft tissue were reported.
Clinical Symptoms and Signs
Pain for months to years
Low-back pain, coccydinia, perineal pain, numbness, constipation, bladder dysfunction, and/or paresthesia of the limbs, secondary to nerve impairment in sacrococcygeal lesions
In spheno-occipital tumors, headache, neck pain, blurred vision, diplopia, weakness, memory loss, emotional instability, or facial nerve palsy, referable to increased intracranial pressure and/or involvement of cranial nerves
Pituitary dysfunction due to destruction of the pituitary gland
An anterior mass in most of sacrococcygeal tumors, rarely accompanied with posterior mass
Image Diagnosis
Radiographic Features
Irregular destruction of the midline of the sacrum, the vertebral body, and clivus, showing osteolysis with or without residual bony trabeculae and amorphous calcification.
Sacral lesions almost always extend into the presacral space.
Destruction of the clivus and sella turcica, extension into the petrous and sphenoid bones, and nasopharyngeal involvement, in the spheno-occipital lesions.
In mobile spine, later involvement of contiguous vertebral bodies and intervertebral disks, with vertebral collapse.
Bone or soft tissue in extra-axial location can be very rarely affected by primary chordoma.
CT Features
Extent of the tumor and soft tissue extension is defined by CT.
Peripheral amorphous calcification in most cases.
MRI Features
Low to intermediate T1-weighted signal intensities.
High T2-weighted signal intensities in the lobulated areas.
Low T2-weighted signal intensities in the septal areas.
MRI demonstrates relationship between the tumor and surrounding structures.
Bone Scan
Practically no abnormal uptake in typical lesions
Image Differential Diagnosis
Giant Cell Tumor
Purely lytic, expansile lesion without soft tissue invasion
Soft tissue extension limited by calcified shell
No amorphous calcification within the lesions
Low T1- and high T2-weighted signal intensities
Significantly increased intensity in gadolinium-DTPA-enhanced T1-weighted images
Different histological pattern
Aneurysmal Bone Cyst
Extraosseous blowout with a sclerotic rim of peripheral ossification
Largely cystic change with fluid-fluid levels (niveau) formation
Involvement of posterior components of the vertebrae
Different histological pattern
Chondrosarcoma
Osteolytic invasive lesion with mottled calcification.
Differentiation between cartilaginous and chondroid neoplasias in the skull base has been controversial.
Cartilaginous-like or chondroid-appearing lesions in the midline related to clivus may be “chondroid” chordoma, while possibility of chondrosarcoma should be considered for an eccentrically located lesion distant from midline in the skull base or clivus.
For differentiation between chondrosarcoma and “chondroid” chordoma, radiological and histological pattern is frequently confusing, and immunohistochemistry may be helpful and mandatory.
Metastatic Carcinoma
Usually suggests a malignant quality of the lesions.
Osteolytic and destructive change mainly located in marrow cavity.
Osteoblastic or mixed lytic and blastic change.
Prostatic adenocarcinoma or neuroendocrine tumor frequently shows purely osteoblastic metastasis.
Metastatic renal cell carcinoma frequently produces purely lytic large destruction with aneurysmal bone cyst-like change.
Florid ossification with pathologic fracture may simulate osteosarcoma.
Radioisotope scintigram bone scan is positive and is useful for finding multiple skeletal metastases.
Different histological pattern.
Meningioma
Intradural and extra-axial/extramedullary lesions with broad dural base
In extracranial location, most commonly seen in the thoracic spine
Isointensity in T1- and T2-weighted images identical to neural elements
Increased intensity in gadolinium-DTPA-enhanced T1-weighted images
Different histological pattern
Pathology
Gross Features
Destructive intraosseous lesion and expansile soft tissue protrusion with pushing margins.
Soft, whitish gray to tan, firm, myxoid or gelatinous in consistency, with lobulated appearance.
Sometimes hemorrhagic, rarely with necrosis and/or cystic change.
Most sacrococcygeal chordomas present with an anterior mass, rarely accompanied with posterior mass.
Tumors at the skull base may invade the paranasal sinus, nasal cavities, or nasopharyngeal spaces.
Very rarely, exact gross relationship between the extraskeletal soft tissue tumor and the sacrum is uncertain.
Histological Features
Lobular arrangement of cellular aggregation separated by fibrous septa in a low magnification.
In a tiny specimen obtained by needle biopsy, identification of the lobulation can be difficult.
Ribbons, chords, or reticular epithelial-like arrangement of tumor cell, with myxoid and slightly bluish stroma, in the cellular lobules.
Faintly eosinophilic or clear cytoplasm with frequent intracytoplasmic bubbly vacuoles, showing “physaliphorous” appearances.
Usually blunt nuclear features.
Immunohistochemically negative for D2-40 and positive for AE1/AE3, CAM5.2, EMA, brachyury, S100 protein, and vimentin.
Chordomas in infants frequently show atypical histologic feature with relentless clinical course.
“Atypical” chordoma, as frequently seen in pediatric patients, histologically shows higher cellularity with sheet-like arrangement and/or spindle cell proliferation, nuclear atypia, or pleomorphic nucleus, even demonstrating sarcomatoid appearances.
In clival lesion, chondroid appearance can be prominent, producing the histologic features of “chondroid” chordoma.
According to recent studies, differentiation between “chondroid” chordoma and genuine chondrosarcoma in the skull base has been controversial.
Dedifferentiated chordoma shows synchronous or metachronous coexistence of typical chordoma and anaplastic spindle/pleomorphic cell sarcoma as seen in dedifferentiated chondrosarcoma.
In contrast to dedifferentiated chondrosarcoma, reported examples of dedifferentiated chordoma may include post-radiation sarcomas after radiation therapy for preexistent chordomas.
Pathologic Differential Diagnosis
Benign Notochordal Tumor/Ecchordosis Physaliphora Spheno-occipitalis
Asymptomatic solitary intraosseous lesion, incidentally found in the base of skull, most common in the clivus, the sacrococcygeal vertebrae, the cervical vertebrae, and the lumbar vertebrae, in this order, sparing the thoracic spine.
Without extraosseous extension.
Permeating the intertrabecular spaces of the vertebral body, frequently with entrapped bone marrow islands.
Intervening bony trabeculae in the lesion are often sclerotic.
Without lobulation, fibrous septa, extracellular myxoid matrix, necrosis, or destructive growth pattern.
Uniform, sheet-like proliferation of bland-looking tumor cells with well-defined cell boundary, resembling fatty marrow at low magnification.
Centrally or peripherally placed round to oval small nuclei, containing small nucleoli and fine nuclear chromatin.
Clear to faintly eosinophilic cytoplasm with various degree of vacuolization, mimicking mature adipocytes, without typical “physaliphorous” cellular features.
Can have eosinophilic cytoplasm, with eosinophilic hyaline globules.
No mitotic figures.
Juxtaposed to a benign notochordal tumor, foci of a chordoma may be found, with sharp transition, suggesting histogenetic relationship between these two tumors.
Immunohistochemically negative for D2-40, positive for S100 protein, EMA, AE1/AE3, CAM5.2, and brachyury.
Ecchordosis physaliphora spheno-occipitalis affects skull base and shows the same morphological features as seen in benign notochordal tumor.
Meningioma
Chordoid meningioma, clear cell meningioma, and even rhabdoid meningioma can histologically mimic chordoma.
Usually accompanied by intradural, extramedullary tumor attached to the dura.
In the paraspinal soft tissue, post-vertebral proliferation is frequent.
Lobular arrangement separated by fibrous connective tissue septa is unusual.
Immunohistochemically positive for EMA and negative for pan-cytokeratin and brachyury.
Myxopapillary Ependymoma
Intradural tumor in the cauda equina region, arising from the filum terminale, with rare extradural occurrence
Without lobulation separated by fibrous septa
Papillary structure to web-like reticular network of cuboidal or flat to even spindle cells, with myxoid to mucinous extracellular materials
Immunohistochemically negative for keratins or brachyury
Chondrosarcoma
Without interlobular fibrous septum, even in tumors showing vague lobulation.
Can show calcification in the center of chondroid lobule-like proliferation.
Immunohistochemically positive for D2-40 and podoplanin and negative for keratins and brachyury.
Sox 9 is positive in chondrosarcoma as well as in chordoma.
In the skull base lesions, differentiation between chondrosarcoma and “chondroid” chordoma is controversial, and immunostainings for brachyury and keratins may be mandatory.
Giant Cell Tumor
Diffuse proliferation of mononuclear neoplastic cells with eosinophilic cytoplasm and ill-defined cell borders makes “hand-in-hand” reticular arrangement.
Large geographic necrosis is frequent.
Xanthogranulomatous change or fibrous histiocytoma-like proliferation can be seen.
Multinucleate giant cell is not a histologic feature of chordoma.
Sometimes, cystic changes with bloody contents showing secondary aneurysmal cyst-like change.
Aneurysmal Bone Cyst
Intraosseous or expansile lesion protruding into soft tissue, without invasion.
Large cystic spaces containing blood.
In the cyst wall and septal tissue between cystic spaces, proliferation of mononuclear cells and spindle cells with multinucleate giant cells showing granulation-like features, frequently accompanied with bone and osteoid formation.
In spine, usually affects the posterior components, with soft tissue protrusion.
“Solid” variant of aneurysmal bone cyst shows granulation-like histology with various degrees of ossification and osteoid formation.
Extraskeletal Myxoid Chondrosarcoma (“Chordoid Tumor”)
Soft tissue sarcoma is usually affecting extra-axial location; very unusual intraosseous variant of extraskeletal myxoid chondrosarcoma, however, has been reported.
Lobular and multinodular arrangement of epithelial-like cells with clear to eosinophilic cytoplasm in the myxoid of mucinous pool, frequently with the so-called “chordoid” appearance.
Without chondrogenic features or calcification.
Immunohistochemically negative for EMA, cytokeratins, brachyury, or S-100 protein.
With characteristic translocation of t(9;22)(q22;q12).
Myoepithelioma/Myoepithelial Carcinoma/Mixed Tumor/Parachordoma
May rarely arise in bone.
Same histologic spectrum as seen in mixed tumor of salivary gland, including ductal structure.
Lobular pattern in low-power field, with strandular or reticular arrangement of epithelial cells in myxoid background in each lobule, may, apparently, simulate chordoma.
Physaliphorous cellular appearance is not typical.
May show cartilaginous or osseous matrix in the stoma.
Immunohistochemically positive for EMA, CK8/18, AE1/3, and S100 protein.
Gene rearrangement of EWSR1/POU5F1 due to t(6;22)(p21;q12), and EWSR1/PBX1 due to t(1;22)(q23;q12).
PLAG1 gene rearrangement in benign myoepithelioma has also been reported.
Osteosarcoma
Usually high-grade, spindle cell or pleomorphic cell sarcoma, with osteoid formation by neoplastic cells.Related posts:
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