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Chondroblastoma

  • AKA “Codman’s tumour”

Definition

  • Benign cartilage lesion
  • But aggressive/ frankly malignant behaviour reported
  • Arises in secondary ossification centre
  • Develops until physis closes

Epidemiology

  • Rare cartilage tumour
  • < 1% of all bone tumours
  • Found in 2nd decade with peak at 20 years
  • M:F – 1.5:1
  • Appears in secondary ossification centre
    • Epiphysis of long bones (cf. Enchondromas in meta-diaphysis)
      • Proximal humerus (Codman’s tumour)
      • Around knee
        • Distal femur
        • Proximal tibia
  • On rare occasions seen in
    • Older patients
    • Odd locations such as spine & flat bones

Clinical Features

  • Adolescent or young adult
  • Pain & swelling
  • Can restrict ROM of joint
  • Confused with intra-articular pathology
  • Can alter the epiphyseal development in young children

Investigations

  • X-ray
    • Well-demarcated lucent defect (ie. radiolucent with sclerotic margin)
    • Epiphyseal in location & eccentric
    • May extend into metaphysis
    • 25-50% have punctate calcification
    • 25% have popcorn or chicken-wire calcification
    • < 10% have periosteal reaction
    • Cortical bone intact or expanded
  • Bone Scan
    • Very hot
  • MRI
    • Oedema seen in surrounding tissues

Pathology

  • Gross
    • Gritty/ Greyish pink material
  • Microscopic
    • Highly cellular & undifferentiated tissue
    • Sheets of Chondroblasts
    • Round & Polygonal cells
    • Bluish cytoplasm
    • Occasional multinucleated cells of osteoclast type
    • Small areas of cartilaginous matrix & extracellular calcification present
    • Chicken wire calcification
    • Atypical cartilage matrix
    • Stains positive for S100
    • Chondroid Matrix
    • Differentiate from
      • GCT by absence of typical spindle stromal cells of GCT
    • 20% are cystic & haemorrhagic similar histologically to ABC

Differential Diagnosis

  • GCT
  • OCD
  • Brodies abscess
  • Clear Cell Chondrosarcoma

Treatment

  • Difficult to irradicate due to anatomic position without damaging joint or physis
  • Intralesional curettage & bone grafting usual approach
  • Often access through growth plate as patient at or near end of growth
    • Ie. preserve the joint rather than growth plate
  • If recurrence occurs then wide resection procedure of choice

Intra-lesional Curettage

  • Technically more feasible
  • Intra-articular exposure required
  • Local Adjuvant Therapy
    • Phenol
    • Liquid Nitrogen
      • Avoid damage to physis if possible
    • Bone graft
  • Recurrence may occur
  • Usually cured with 2nd curettage

Wide Resection

  • Lower recurrence rate
  • Usually not possible without loss of function
  • Indicated for 2nd recurrence
  • There is incidence of pulmonary lesions which are rimmed with bone & should be excised
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