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Sacral Chordoma

Summary

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  • Rare malignant tumour arising from notochordal remnants, typically presenting in the sacrococcygeal region with insidious onset of lower back pain and neurological symptoms
  • Characterised by locally aggressive growth with high recurrence rates, composed of physaliferous cells in a myxoid matrix
  • Imaging demonstrates a large, lobulated, destructive sacral mass with high T2 signal intensity and heterogeneous enhancement1

Pathophysiology

  • Arises from embryonic notochordal remnants along the axial skeleton
  • Slow-growing but locally aggressive tumour with infiltrative growth pattern
  • Composed of characteristic physaliferous (bubble-bearing) cells containing intracytoplasmic vacuoles
  • Produces abundant extracellular myxoid matrix rich in mucopolysaccharides
  • Expresses brachyury (T-gene product), a specific marker for notochordal differentiation
  • Three histologic subtypes:
    • Conventional (most common)
    • Chondroid (better prognosis)
    • Dedifferentiated (worst prognosis)

Demographics

  • Accounts for 1-4% of all primary bone malignancies
  • 50-60% occur in sacrococcygeal region
  • Peak incidence in 5th-7th decades of life
  • Male predominance (2:1 ratio)
  • Rare in children and adolescents
  • No specific ethnic predilection
  • Familial chordoma accounts for <5% of cases (associated with duplications of brachyury gene)

Diagnosis

  • Clinical presentation:
    • Insidious onset of lower back pain (months to years)
    • Constipation and bowel dysfunction
    • Urinary incontinence or retention
    • Lower extremity weakness and numbness
    • Palpable presacral mass on rectal examination
  • Laboratory findings:
    • No specific serum markers
    • Elevated alkaline phosphatase may be present
  • Histopathology:
    • Physaliferous cells with vacuolated cytoplasm
    • Lobulated architecture separated by fibrous septa
    • Myxoid stroma
    • Immunohistochemistry positive for:
    • Brachyury (highly specific)
    • Cytokeratin
    • EMA (epithelial membrane antigen)
    • S100 protein

Imaging

  • Plain radiography:
    • Large lytic sacral mass with bone destruction
    • Calcifications in 30-70% of cases
    • Anterior soft tissue mass
  • CT:
    • Midline destructive sacral mass
    • Mixed lytic and sclerotic bone changes
    • Intratumoural calcifications
    • Well-defined soft tissue component
  • MRI (modality of choice):
    • T1: Hypointense to isointense relative to muscle
    • T2: Markedly hyperintense (due to high mucin content)
    • T1+C: Heterogeneous moderate enhancement with honeycomb pattern
    • DWI: Variable restricted diffusion (ADC values typically intermediate)
    • STIR: Hyperintense signal
    • Sagittal imaging crucial for surgical planning
  • Key imaging features:
    • "Mushroom-shaped" configuration extending anteriorly into pelvis
    • Lobulated contours with internal septations
    • Involvement of multiple sacral segments
    • Preservation of intervertebral disks (unlike metastases)
  • PET/CT:
    • Mild to moderate FDG uptake
    • Useful for detecting metastases and recurrence

panels-1

  • A 50-year-old patient presented with sphincter disturbance and lower back pain.
  • MRI showed a lobulated minimally enhancing T2-hyperintense lesion centred on the sacrum.
  • CT showed loss of normal cortex.
  • A CT-guided biopsy confirmed a sacral chordoma.

Treatment

  • En bloc sacrectomy with wide margins is the mainstay, with adjuvant proton/carbon-ion radiotherapy; local recurrence is common. The very high T2 signal and preservation of disc spaces (unlike metastases) are key clues

Differential diagnosis

Differential diagnosis Differentiating feature
Giant cell tumour Eccentric location, typically spares the midline; lacks calcifications; may have ABC-like areas with fluid-fluid levels
Chondrosarcoma Often arises from sacroiliac joint; contains chondroid matrix with rings-and-arcs calcification pattern; lower T2 signal than chordoma
Metastases Multiple lesions; usually more aggressive bone destruction; may have primary at another site on systemic imaging
Plasmacytoma/Myeloma Punched-out lytic lesions on CT; typically spares disc spaces; diffuse marrow involvement on MRI
Neurogenic tumour Arises from sacral foramina; expands neural foramen; smooth remodelling rather than destruction
Osteosarcoma Aggressive periosteal reaction; osteoid matrix production; mixed lytic-sclerotic pattern
Ewing sarcoma Permeative pattern with aggressive periosteal reaction; disproportionately large soft tissue mass; no calcifications
Lymphoma Permeative pattern with relative preservation of cortex; soft tissue mass disproportionate to bone destruction
Aneurysmal bone cyst Fluid-fluid levels on MRI; expansile with thin cortical shell; no solid enhancing component
Sacral meningioma Intradural location; dural tail sign; homogeneous enhancement; no bone destruction

  1. Radaelli et al. The sacral chordoma margin. 2020. European journal of surgical oncology : the journal of the European Society of Surgical Oncology and the British Association of Surgical Oncology - Open in new tab. ↩