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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 enhancement

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

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  • 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

  • Surgical management:
    • En bloc resection with wide margins (primary treatment)
    • Sacrectomy (partial or total depending on tumour extent)
    • Negative margins crucial for reducing recurrence
    • High sacral tumours (above S3): better functional outcomes
    • Low sacral tumours (below S3): higher risk of bowel/bladder dysfunction
  • Radiation therapy:
    • Adjuvant radiation for positive margins or subtotal resection
    • High-dose photon or proton beam therapy
    • Carbon ion therapy showing promising results
    • Doses typically 60-70 Gy or higher
  • **

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