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Updated: Mar 31 2023

Non-Ossifying Fibroma

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Images
https://upload.orthobullets.com/topic/8027/images/Case B - femur - xray - Parsons_moved.png
https://upload.orthobullets.com/topic/8027/images/Case B - femur - bone scan - Parsons_moved.png
https://upload.orthobullets.com/topic/8027/images/5a_moved.jpg
https://upload.orthobullets.com/topic/8027/images/Histology A - low power - Parsons_moved.jpg
https://upload.orthobullets.com/topic/8027/images/Histology B - high power - Parsons_moved.jpg
https://upload.orthobullets.com/topic/8027/images/Histology C - low power - Parsons_moved.jpg
  • summary
    • Non-Ossifying Fibromas are benign fibrogenic lesions that result from dysfunctional ossification that are most commonly found in the metaphysis of long bones. Patients typically present between the ages of 5 and 15 with an asymptomatic lesion discovered incidentally on radiographs.
    • Diagnosis is made on radiographs with a characteristic metaphyseal eccentric "bubbly" lytic lesion surrounded by a sclerotic rim.
    • Treatment is observation as most lesions resolve spontaneously.
  • Epidemiology
    • Incidence
      • occurs in 30-40% of skeletally immature children
    • Demographics
      • more common in males (2:1)
      • common in children 5-15 years old
    • Anatomic location
      • metaphysis of long bones
      • 80% in lower extremity
        • distal femur > proximal tibia > distal tibia
        • uncommon in proximal femur, proximal humerus
  • Etiology
    • Mechanism
      • non-ossifying fibroma (NOF) is a benign fibrogenic lesion that is related to dysfunctional ossification
        • one of the most common benign bone tumors in childhood (with osteochondroma)
        • other names
          • metaphyseal fibrous defect
          • nonosteogenic fibroma
          • cortical desmoid
          • fibrous cortical defect
          • fibromatosis
          • fibroxanthoma
    • Pathophysiology
      • possibly due to abnormal osteoclastic resorption at the subperiosteal level during remodeling of the metaphysis
    • Associated conditions
      • Jaffe-Campanacci syndrome
        • congenital syndrome of multiple non-ossifying fibromas and
          • cafe au lait pigmentation
          • mental retardation
          • heart, eyes, gonads involved
      • neurofibromatosis
      • familial multifocal NOF
      • ABC
  • Presentation
    • Symptoms
      • asymptomatic
        • usually found incidentally
      • may present with pathologic fracture
  • Imaging
    • Radiographs
      • diagnostic
      • metaphyseal eccentric "bubbly" lytic lesion surrounded by sclerotic rim
        • cortex may be expanded and thin
        • length > width
      • as bone grows
        • migrates to diaphysis
        • lesions enlarge (1-7cm)
      • as patient approaches skeletal maturity, lesions become sclerotic
      • avulsion of adductor magnus insertion in the posteromedial aspect of the distal femur may produce a similar looking lesion
    • CT
      • quantitative CT shown to be useful in predicting fracture risk
  • Studies
    • Histology
      • classic characteristics are
        • fibroblastic spindle cells in whirled or storiform pattern (helicopter in wheat field)
        • fibroblastic connective tissue background
        • numerous lipophages and giant cells
        • hemosiderin pigmentation
        • occasional ABC component
  • Differential
    • Giant cell tumor
      • painful
      • rare in skeletally immature
      • no mineralization
    • Osteosarcoma
      • painful
      • irregular zone of bony destruction with less defined zone of transition
      • periosteal reaction
      • mineralized soft tissue mass
      • Differential of non-Ossifying Fibroma
      • "Bubbly" lytic lesion on xray
      • Hemosiderin seen on Histology
      • Treatment is Observation alone
      • NOF
      • o
      • o
      • o
      • ABC
      • o
      • UBC
      • o
      • PVNS
      • o
      • Fibrous dysplasia
      • o
      • Enchondroma
      • o
      • Osteochondroma
      • o
      • Eosinophillic granuloma
      • o
      • Paget's
      • o
  • Treatment
    • Nonoperative
        • indications
          • first line of treatment
          • most lesions resolve spontaneously and progressively reossify as child enters 2nd and 3rd decade of life
        • technique
          • radiographs at 6 and 12 months, then annually until reossified
      • casting
        • indication
          • pathologic fracture
          • can be treated as per the fracture alone (long leg casting for distal femur pathologic fx)
    • Operative
      • curettage and bone grafting
        • indication
          • symptomatic and large lesion (> 50-75% cortical involvement)
          • increased risk of fracture shown on quantitative CT
  • Complications
    • Pathologic fracture
      • incidence
        • 90% occur in the lower extremity
          • 50% occur in the distal tibia
      • risk factors
        • >50% involvement of transverse diameter
        • >33mm length in weight-bearing bones (femur and tibia)
      • treatment
        • cast immobilization
          • indications
            • nondisplaced fractures
  • Prognosis
    • Usually spontaneously resolves
    • No malignant or metastatic potential
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