Case of the Month August, 2010, Page 3

Answer

  • Aneurysmal Bone Cyst

Findings

  • CT demonstrates large, lytic lesion centered at L2 with areas of cortical thinning and breakthrough.¬†Internal patchy hyperdensities representing fluid-fluid levels and hemorrhage
  • MRI exam confirms multiple fluid-fluid levels most notable on T2 weighted sequences as well as involvement of the pedicle and vertebral body best appreciated on the axial cut

Differential Diagnosis

  • Unicameral Bone Cyst
  • Aneurysmal Bone Cyst (ABC)
  • Mets
  • Telangiectatic Osteosarcoma

Diagnosis

  • Aneurysmal Bone Cyst (ABC)

Aneurysmal Bone Cyst

  • Benign lesion characterized by cyst-like walls of fibrous tissue filled with blood
  • Can be easily mistaken for malignant neoplasm (pathologically and radiographically)
  • Represents neither cyst nor neoplasm
  • Represents reparative process triggered by tumor or trauma induced vascular process
  • Primary ABC
    • Arises de-novo in bone without recognizable pre-existing lesion
    • Can be caused by trauma
  • Secondary ABC
    • Arises in preexisting lesion (benign or malignant neoplasm)
    • Benign tumors: Giant cell tumor, osteoblastoma, chondroblastomas, fibrous dysplasia
    • Malignant tumors: Osteosarcoma, chondrosarcoma, malignant fibrous histiocytoma (MFH)
  • Epidemiology: 6% of primary bone lesions
  • Most common signs/symptoms: Progressive pain and swelling
  • Clinical profile
    • Rapid increase of pain over 6-12 weeks
    • Spinal lesions may cause cord compression (radiculopathy, quadriplegia), nerve root impingement
    • Scoliosis: 10%
    • Pathologic fracture: 20%
    • Limited range of motion if close to joint
    • History of trauma

 

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