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Osteogenic Tumours

  • Recognise matrix as woven bone ( osteoid )
  • osteoid osteoma & osteoblastoma have similar histology, but different clinical, radiological & gross pathological findings
  • Stroma:
    • fibrovascular = benign
    • sarcomatous = malignant

Benign

Epiphyseal

None Characteristic

Metaphyseal and Diaphyseal

Osteoid osteoma    [Back To Top] 
Small, benign, solitary painful lesion of bone seen mainly in children and adolescents
Aetiology - Unknown
Incidence

  • Accounts for 10% of benign bone tumours
  • Male : Female 2:1
  • Peak age 5 - 25 years (85% in this range)
  • Rare over 40 years
  • Location:

Any bone, rarely multifocal
            tibia & femur in 50%
            spine - posterior elements
            Only occurs in bones formed by endochondral ossification
            May affect any part of a bone but is usually intracortical
Clinically

  • Pain is the commonest presentation
  • Pain often worse at night and relieved by aspirin (more likely NSAIDs now as aspirin not given to kids but the classical description remains)
  • 10% occur in the spine and may -> scoliosis
  • Other sites may -> joint effusion, LLD, synovitis
  • Runs a self limiting course but usually -> surgery for pain relief
  • Pain usually decreases as the lesion matures lasting 18 - 30 months
  • Lesion healed by 3 - 7 years

X-Rays

  • Lytic nidus surrounded by sclerotic bone (which may mask the nidus)
  • Centre of nidus may be calcified
  • CT or tomograms -> diagnosis
  • Hot spot on bone scan

Differential Diagnosis

  1. Bone island (enostosis)
  2. Brodie's abscess
  3. Osteoblastoma
  4. fatigue fracture

Pathology

  • Nidus usually less than 1cm diameter, most less than 0.5cm
  • Nidus composed of thick vascular bars of osteoblastic tissue surrounded by vascular fibrous tissue finally surrounded by mature reactive cortical bone
  • Contains fibroblasts, osteoblasts and osteoclasts, no marrow element
  • May have a calcified centre in the nidus

View some Pathology Pictures
Treatment

  • NSAIDs
    • relieves symptoms
    • may take 3-4 years for symptoms to resolve
  • Surgical:
    • Nidus excision -> no recurrence (need only intact rim of reactive bone around the nidus to ensure complete excision)
    • Intraoperative localisation with:
      1. Bone scan
      2. Tetracycline (4mg tetracycline per kg qid 1-2 days pre operatively -> specimen excised under UV light)
      3. CT
      4. X-Ray excised tissue -> contains nidus
    • Beware the dumbbell nidus
  • Percutaneous radiofrequency coagulation
    • involves percutaneous insertion of a biopsy needle under CT scan guidance
    • a tissue biopsy is taken in order to prove that the needle is properly located
    • then a radiofrequency electrode with a 5 mm exposed tip is introduced thru the cannula
    • the electrode is connected to a radiofrequency generator which raises the temperature of the tip to 90 deg C (which is maintained for 6 minutes)
    • as noted by Rosenthal et al 1998 , results of this technique are comparable to the standard open technique


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