Synonyms

Notochordal tumour (related entity: Benign notochordal cell tumour)

Category

Bone

Behaviour

Malignant

Grade

Low

Gender

Male

Tissue of Origin

Notochord remnant

Epidemiology

• Rare, 3–4% of primary Bone tumours
• Peak incidence in 4th–7th decades
• Male predominance (2:1)
• Three main sites: sacrococcygeal (50%), spheno-occipital (35%), mobile spine (15%)

Clinical Features

• Sacrococcygeal: Low back pain, constipation, urinary symptoms, gluteal mass
• Clivus/skull base: cranial nerve palsies, headache
• Mobile spine: myelopathy, radiculopathy
• Slow-growing but locally destructive

Location

• Sacrum and coccyx (most common)
• Clivus/spheno-occipital region
• Cervical spine (C2 most common in mobile spine)

Imaging

• Midline lytic destructive lesion with soft tissue mass
• CT: calcifications within lesion
• MRI: High T2 signal (myxoid matrix), heterogeneous enhancement
• Sacral lesion: presacral soft tissue mass

Pathology

• Lobulated tumour with physaliferous (vacuolated) cells
• Myxoid intercellular matrix
• S100, brachyury (T gene) positive
• Three subtypes: classic, chondroid, dedifferentiated

Genetics

• TBXT (T/brachyury) germline duplications in familial cases
• Somatic TBXT overexpression
• PI3K/mTOR pathway alterations
• CDKN2A deletions common

Treatment

• Wide surgical resection - en bloc with negative margins paramount
• Proton beam radiotherapy - preferred for skull base and when margins positive
• Carbon ion radiotherapy - superior local control in some centres
• Systemic therapy limited: imatinib (PDGFR-directed) modest activity; clinical trials

Prognosis

• Median survival 6–7 years
• Local recurrence is the dominant mode of failure
• 5-year survival 65–70%
• Dedifferentiated chordoma: very poor prognosis

Key Points

• Brachyury (T protein) IHC is Highly sensitive and specific for chordoma
• Proton beam radiotherapy is treatment of choice for skull base chordoma
• Sacral resection requires detailed preoperative planning for sphincter preservation
• Dedifferentiated variant has sarcomatous component and is Highly aggressive

Workup - Blood Tests

• FBC, U&E, LFTs - pre-operative baseline
• Bone profile - calcium, phosphate, ALP

Workup - Local Imaging

• Plain radiograph
• MRI primary site with gadolinium

Workup - Biopsy

• CT-guided core needle biopsy - planned to avoid contamination of surgical field
• Immunohistochemistry: brachyury (T-box protein)+, S100+, EMA+, CK+
• Brachyury IHC is Highly sensitive and specific for chordoma
• Exclude metastatic carcinoma, chondrosarcoma, and ecchordosis physaliphora

Workup - Staging

• CT chest/abdomen/pelvis - metastases in 5–10% at presentation (lungs, liver, Bone)
• PET-CT

Workup - Other

• MDT at specialist Bone sarcoma or skull base centre
• Neurosurgical and orthopaedic spine surgery liaison essential

Follow-up Summary

• Post-op visit at 6 weeks
• Year 1: post-operative visit in first 6 weeks; 3 - 6 monthly clinical examination and CXR; MRI of primary site at 6 months, 1 year, 2 years. Sacral/skull base chordoma: MRI spine/skull base 6-monthly for 5 years; CT chest annually
• Years 3–5: 6-monthly review and CXR; annual MRI primary site
• Years 6–10: Annual review, CXR and MRI primary site
• Local recurrence is the dominant mode of failure - vigilant local imaging essential
• Discharge at 10 years; advise self-monitoring due to Slow-growing nature and late recurrence