Pediatric Osteochondroma

  • Etiology:
    — Benign bony growth covered by cartilage cap caused when piece of growth plate separates and lays down cartilage off of normal axis of development
    — Can be caused by radiation therapy and such lesions are at higher risk for malignant degeneration
  • Imaging:
    — Location: Usually is metaphysis of tubular long bones or costochondral junction (metaphyseal equivalent) with excresense away from metaphysis and growth plate
    — Lytic or blastic: Cartilage-capped bone projection, sessile or pedunculated cystic growth on bony stalk
    — Matrix: (chondroid, osteoid, fibrous)
    — Zone of transition: Narrow
    — Periosteal new bone or cortical destruction: None
    — Additionally:
  • Imaging US: Cartilaginous cap is hypoechoic with internal echogenicity similar to normal epiphyseal cartilage
  • DDX:
  • Complications: 1-2% degenerate into chondrosarcoma
  • Treatment:
  • Clinical:
    — Presents as hard, mobile mass that may cause pain due to fracture or nerve compression or malignant degeneration
    — May cause vascular compression
    — Most common benign bone tumor
    — Rarely arise from ribs

Radiology Cases of Osteochondroma

Radiograph of osteochondroma
AP (left) and lateral (right) radiographs of the knee show a pedunculated cartilage-capped lesion on a bony stalk in the metaphysis of the femur that is growing away from the physis.
Radiograph of multiple osteochondromas of the knee
AP radiograph of the knees shows bilateral lesions arising from the medial aspect of each tibial metaphysis, with a bony stalk growing away from the metaphysis with a lytic lesion growing at the tip of each stalk with a narrow zone of transition and no associated periosteal reaction.
CXR and CT of osteochondroma of the rib
CXR PA shows a calcific density in the head of the left third rib. Contiguous images from an axial CT without contrast of the chest shows a bony outgrowth at the proximal aspect of the left third rib posteriorly.