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Case of the Week 243

What's the most likely diagnosis?

  • 21 year-old with lump near knee

  1. Osteoblastoma
  2. Osteochondroma
  3. Osteosarcoma
  4. Chondroblastoma
  5. Giant Cell Tumor



2. Osteochondroma



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General Considerations

  • Osteochondroma is the most common benign bone tumor and the most common skeletal neoplasm
    • They account for approximately 35% of all benign bone tumors and 9% of all bone tumors
  • They are cartilage-capped bony projections from the external surface of a bone
  • They occur only in bones which form by enchondral bone formation and most commonly found around the knee (40%) and shoulder, although they can occur in any bone
  • Almost all are diagnosed in patients under the age of 20 with a marked male:female predominance (3:1)
  • They grow until skeletal maturity and then stop growing when the epiphyseal plate fuses, although the cartilage cap can continue to grow slowly until about age 30
  • Osteochondromas tend to occur near an epiphyseal growth plate and grow away from the physis


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