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Updated: Jun 9 2024

Aneurysmal Bone Cyst

Images A - femur - xray - parsons_moved.png C - calc - xray - parsons_moved.png C - calc - ct- parsons_moved.gif C - calc - MRI b - parsons_moved.gif A_moved.png
  • summary
    • Aneurysmal Bone Cysts are benign, non-neoplastic, reactive bone lesions that most commonly occur in the femur and tibia. The condition typically presents in patients less than 20 years of age with focal pain and swelling. 
    • Diagnosis is made with radiographs showing an expansile, eccentric, and lytic lesion with bony septae and a biopsy showing blood-filled spaces without endothelial lining.
    • Treatment is usually nonoperative for lesions associated with a fracture. Aggressive curettage, with adjuvant treatment and bone grafting, is indicated for symptomatic lesions without associated fracture. 
  • Epidemiology
    • Demographics
      • 75% of patients are < 20 yrs.
    • Anatomic location
      • >60% in long bones (Femur and tibia being most common)
      • 51% occured in the lower extremities, 22.5% in upper extremities
      • usually in metaphysis
      • metatarsal and calcaneus are the most common locations in the foot
      • posterior elements of pelvis
      • may be found in similar location as telangiectatic osteosarcomas
  • Etiology
    • Pathophysiology
      • primary and secondary forms
        • primary ABC
          • driven by upregulation of the ubiquitin-specific protease USP6 (TRE17-USP6when combined by a translocation with a promoter pairing
          • most commonly described translocation TRE17-USP6
        • secondary ABC
          • not considered a neoplasm because no known translocation has been identified
    • Associated conditions
      • associated with other tumors 30% of time
        • giant cell tumor
        • chondroblastoma
        • fibrous dysplasia
        • chondromyxoid fibroma
        • NOF
  • Presentation
    • Symptoms
      • pain and swelling
      • may present with pathologic fracture
    • Physical exam
      • neurologic deficits possible with spine lesions
  • Imaging
    • Radiographs
      • expansile, eccentric and lytic lesion with bony septae ("bubbly appearance")
      • usually in metaphyseal
      • classic cases have thin rim of periosteal new bone surrounding lesion
      • no matrix mineralization
    • MRI or CT scan
      • will show multiple fluid lines
      • lesion can expand into soft tissue
  • Studies
    • Histology
      • Characteristic findings
        • cavernous space
        • blood-filled spaces without endothelial lining
      • cavity lining
        • numerous benign giant cells
        • spindle cells
        • thin strands of woven (new) bone present
  • Differential
    • Radiographic differential includes
      • UBC
      • telangiectatic osteosarcoma
    • Histologic differential includes
      • telangiectatic osteosarcoma
      • giant cell tumor
        • Differential of Aneurysmal Bone Cyst
        • "Bubbly" lytic lesion on xray
        • "Lakes of Blood" on histology
        • Treatment is curettage and bone grafting 
        • Aneurysmal Bone cyst
        • o
        • o
        • o
        • UBC
        • o
        • NOF
        • o
        • Giant Cell Tumor
        • o
        • Chondroblastoma
        • o
        • Chondromyoid fibroma
        • o
        • Osteoblastoma
        • o
        • Telangiectatic osteosarcoma
        • o
  • Treatment
    • Nonoperative
      • nonoperative fracture management
        • indications
          • ABC with acute fracture
            • indicated until fracture has healed. Once healed, treat as an ABC without fracture unless the fracture has led to spontaneous healing of the ABC
    • Operative
      • aggressive curettage (+/- adjuvant) and bone grafting
        • indications
          • symptomatic ABC without acute fracture
        • technique
          • possible adjuvants
            • phenol
            • argon beam
            • liquid nitrogen
        • outcomes
          • local recurrence in up to 25% and more common in children with open physes
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