Chordoma
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Direct answer
Chordoma is a slow-growing malignant tumour arising from remnants of the notochord, and it lies along the midline of the sacrum, clivus and vertebral bodies. Its defining histological feature is the physaliphorous cell, a cell with bubbly, vacuolated cytoplasm. Treatment is wide en bloc resection followed by radiotherapy, because chordoma responds poorly to chemotherapy and recurs locally when margins are narrow.
What you must remember
- Origin: remnants of the notochord, which explains the midline location along the axial skeleton.
- Site: the sacrum and sacrococcygeal region most often, followed by the clivus at the skull base and the vertebral bodies.
- Histology: physaliphorous cells with vacuolated cytoplasm set in a lobulated, myxoid matrix.
- Immunohistochemistry: positive for cytokeratin, EMA and S-100 protein, with nuclear brachyury, a transcription factor linked to notochordal lineage, being especially useful.
- Imaging: a lobulated, expansile lesion that is bright on T2 MRI, often with calcification on CT.
- Treatment: en bloc wide resection, with proton or carbon-ion radiotherapy in selected cases because conventional radiotherapy is less effective.
- Behaviour: locally aggressive and slow, with late lung metastases in a minority of patients.
A staged pathway for a sacral chordoma
A sacral mass in an adult that causes buttock pain or bladder symptoms can be a chordoma, and the work-up must be planned before any operation. Each step shapes the surgical field, so the sequence matters as much as the individual tests.
- Map the tumour on MRI: Contrast MRI defines the extent into the presacral soft tissue, the sacral nerve roots and the pelvic viscera.
- Stage the chest: A CT chest looks for pulmonary metastases, which are uncommon at presentation but important to exclude.
- Biopsy along the planned route: Image-guided or open biopsy is placed so that the tract can be excised with the tumour.
- Plan en bloc resection: A wide resection through normal tissue usually needs a multidisciplinary team, including spine, colorectal and plastic surgeons for sacral lesions.
- Add radiotherapy: Proton or carbon-ion radiotherapy to the tumour bed is used when margins are narrow or positive.
- Surveil for recurrence: Long-term MRI is needed because local recurrence is common and can appear many years after surgery. Recurrence is usually managed by re-resection where feasible, with further radiotherapy in selected cases.
Where the exam tries to catch you
Most lost marks come from choosing the wrong primary treatment or misreading a midline lesion.
- Trap: choosing chemotherapy as the main treatment Correct: chordoma is largely chemoresistant, so surgical resection with radiotherapy remains the core of care.
- Trap: biopsying through a route that cannot be excised Correct: the biopsy tract must lie in the surgical field because tumour cells can seed along it.
- Trap: labelling a clival mass as a meningioma without considering chordoma Correct: clival chordomas are midline, often destroy bone and show brachyury positivity, which supports the diagnosis.
Frequently asked questions
Which immunohistochemical marker is most useful for diagnosing chordoma?
Nuclear brachyury is the marker most useful for diagnosing chordoma, because it reflects notochordal lineage. Cytokeratin and S-100 protein are also positive in most cases but are less specific. The diagnosis still rests on combined histology, immunohistochemistry and imaging.
Why does chordoma commonly arise in the sacrum and clivus?
Chordoma commonly arises in the sacrum and clivus because notochordal remnants persist at the two ends of the axial skeleton. Sacral tumours often grow silently and become large before they are diagnosed. Clival tumours present with cranial nerve palsies or headache.
Why is radiotherapy used after resection of chordoma?
Radiotherapy is used after resection of chordoma because the tumour is relatively radioresistant to conventional photon treatment, and recurrence is common at narrow margins. Proton or carbon-ion beams deliver higher doses to the tumour bed while sparing nearby neural structures. The aim is local control, since chordoma rarely responds to chemotherapy.
What does chordoma look like on imaging?
Chordoma typically appears as a lobulated, expansile lytic mass that is hyperintense on T2 MRI, often with septations and calcification on CT. In the sacrum it can extend into the presacral space. Its appearance can resemble other destructive lesions, so biopsy is needed to confirm the diagnosis.
Is chordoma a benign or malignant tumour?
Chordoma is malignant, although it is locally aggressive and slow-growing and is often described as low-grade malignant. Distant metastasis is uncommon at first presentation. Late local recurrence and late lung metastases are the main long-term concerns.