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Flashcards in Reactive lesions Deck (14):

What are unicameral bone cysts?

  • Aka simple bone cysts
  • a non neoplastic, serous fluid bone lesion though to result from temporary failure of medullary bone formation near the physis
  • pts <20 yrs
  • location
    • proximal humerus- usually
    • prox fem, distal tibia, ilium, calcaneus, MC, distal radius
    • metaphysis adj to physis
    • progresses towards diaphysis w bone growth

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What is the prognosis of unicameral bone cysts?

  • As pt approaches skeletal maturity bone cyst will 
  • decrease in size and may heal after growth complete
  • fx healing doesn't -> cyst resolution
  • Follow up in active phase due to recurrence and risk of fx or growth arrest


What are the classification of unicameral bone cysts?

  • Active
    • if cyst is adjacent to physis
  • Latent 
    • if normal bone separates cyst from physis- see pic

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What are the symptoms of unicameral bone cysts?

  • Aysymptomatic unless fx
  • Pain from path fx -50%


What is seen on radiographs with unicameral bone cysts?

  • Central, lytic, well demarcated metaphyseal lesion
    • 2-3 % cross physis
  • Cystic expansion w symmetrical thinning of cortices
  • Fallen leaf sign - path fx with fallen cortical fragment in base of empty cyst
  • MRI- v dark on T1, very bright T2
  • Bone scan variable, usually warm

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What is seen on histology of unicameral bone cysts?

  • Cyst with Thin fibrous lining containing fibrous tissue, giant cells and haemosiderin pigment 

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What is the ddx if a unicameral bone cysts?

  • Aneurysmal bone cyst
    • more expansile than UBC
    • UBC is usually not wider than physis
  • Telangiectatic osteosarcoma


What is the tx of unicameral bone cysts?

Non operative

  • immobilzation alone
    • prox humeral path fx
    • 15% lesions will fill in w native bone after acute fx
  • Aspiration/methylprednisolone acetate injection
    • active cysts in prox humerus
    • usually several injections esp in v young kids


  • Currettage and bone grafting+/- internal fixation based on tumour location
    • latent cysts as risk of fx/osteonecrosis
    • prox femoral lesions- path fx-> high rate refx and malunion when tx nonop.
    • avoid in active lesions as communication w physis may-> growth arrst


What is an aneurysmal bone cyst?

  • A Benign and non neoplastic reactive bone lesion filled with multiple blood-filled cavities
  • can be locally destructive to normal bone
  • may extend into softt tissue
  • 75% pts are <20 yrs
  • location
    • ​25% spine
    • 20% long bones
    • usually Metaphysis
    • post elements of pelvis
  • types
    • ​primary ABC
      • now known neoplasm due to upregualtion of ubiquitin-specific protease USP6 gene on 17p13 
    • Secondary ABC
      • not neoplastic - no translocation

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Any associated conditions of aneurysmal bone cyst?

what is the prognosis of aneurysmal bone cyst?

  • Assoc with Other tumours 30% time
  • Giant cell tumour
  • chondroblastoma
  • fibrous dysplasia
  • chondromyxoid fibroma
  • NOF


  • Good


Describe the symptoms of aneurysmal bone cyst?

  • Pain and swelling
  • Path fx
  • neurological deficit possible w spinal lesions


What is seen on imaging of aneurysmal bone cyst

  • Expansile, eccentric, lytic lesion with Bony septae= Bubby appearance
  • Usually in metaphyseal bone
  • thin rim perosteal new bone around lesion
  • no matrix mineralisation
  • MRI
    • multiple fluid lines - see pic
    • lesion can expand into soft tissue

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What is the histology of aneurysmal bone cyst?

  • Cavernous space
  • blood filled spaced without endothetial lining
  • cavity lining
    • ​numerous benign giant cells
    • spindle cells

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What is the tx for aneurysmal bone cyst?

Non operative

  • non operative fx management
    • ABC w acute fx
    • indicated until fx healed. once healed, tx as an ABC withouf fx, unless fx-> spontanous healing of ABC


  • Aggressive curettage and bone grafting
    • symptomatic ABC without fx
    • some use adjuvant tx ( phenol)
    • local reoccurance up to 25%, more common in children w open physes