osteochondroma; osteocartilagenous exostosis; osteochondromatosis

Etiology

• unknown
• does not result from injury

Epidemiology

• develops during childhood or adolescence
  • teenagers & young adults
• soliary osteochondromas represent 35-40% of benign bone tumors

Pathology

• benign bone tumor often arise near the metaphyses of bone
• abnormal growth that forms on the surface of a bone near the growth plate
• neoplasm consist of both bone & cartilage
• growth of neoplasm generally stops with skeletal maturity
• may be single tumor (osteocartilagenous exostosis) or multiple tumors (osteochondromatosis)
• rarely cause pathological fractures

Genetics

• associated with defects in EXT1
• see hereditary multiple exostoses

Clinical manifestations

• generally asymptomatic
• painless lump near a joint
  • knee & shoulder most often involved.
  • distal femur is most common location
• pain with activity
  • osteochondroma located under a tendon
  • the tendon moving over an osteochondroma may result in pain
• paresthesia
  • tumor may put pressure on a nerve, such as behind the knee
• changes in blood flow tumor may compress a blood vessel

Laboratory

• bone biopsy is osteosarcoma suspected

Radiology

• X-ray of long bones
  • outgrowth may have a stalk or stem that sticks out from normal bone
  • generally appear as a bone spur arising from the external surface of bone pointing away from the adjacent (knee) joint
• computed tomography
• magnetic resonance imaging
  • a thick covering of cartilage over the tumor is suspicious for malignant transformation

Differential diagnosis

• chondrosarcoma

Management

• generally, no treatment required

More general terms

• chondroid neoplasm (cartilage neoplasm)
• bone neoplasm
• osteochondropathy (disorder of bone & cartilage)

More specific terms

• hereditary multiple exostoses (diaphyseal aclasis)

Additional terms

• chondroma; enchondroma