title: Primary hemangiopericytoma in the axis bone: case report and review of literature.
abstract: OBJECTIVE
  To the best of our knowledge, this is the first reported case of primary hemangiopericytoma in the axis bone. With this report, we attempt to better characterize this uncommon lesion in the vertebral column.
  
  
  METHODS
  This report describes a case of primary heman-giopericytoma in the axis bone of a 16-year-old female patient who presented with acute torticollis. Her neurological status was unimpaired. A lateral radiograph of the cervical spine demonstrated an odontoid neck fracture and a C1-C2 rotatory deformity. The magnetic resonance imaging study showed a hypodense lesion with moderate enhancement on T1- and T2-weighted images on the dens and body of the axis with an odontoid neck fracture. Reviewing the literature, primary hemangiopericytoma in the spine is rare; 9 cases of hemangiopericytoma with vertebral bone involvement and 44 cases of this tumor with intraspinal meningeal involvement have been reported.
  
  
  METHODS
  The patient was treated with odontoidectomy via the transoral approach, along with posterior fixation using the Halifax clamp. She was followed up 17 months after surgery, and no evidence of tumor recurrence was found.
  
  
  CONCLUSIONS
  The treatment for osseous hemangiopericytoma is still controversial. At present, adequate surgical removal with postoperative radio-therapy is recommended. In addition, although hemangiopericytoma is rare in the spine, it should be kept in mind in the differential diagnosis of spinal tumors.
authors.affiliation: Department of Neurosurgery, Taiwan Provincial Tao-Yuan Hospital, Republic of China.
authors.forename: Y J
authors.initials: YJ
authors.lastname: Lin
authors.forename: Y K
authors.initials: YK
authors.lastname: Tu
authors.forename: S M
authors.initials: SM
authors.lastname: Lin
authors.forename: C T
authors.initials: CT
authors.lastname: Shun
mesh_terms: D000293:Adolescent; D005260:Female; D005500:Follow-Up Studies; D006393:Hemangiopericytoma / Q000175:diagnosis / Q000601:surgery*; D006801:Humans; D008279:Magnetic Resonance Imaging; D009809:Odontoid Process / Q000473:pathology / Q000601:surgery*; D013123:Spinal Fusion; D013125:Spinal Neoplasms / Q000175:diagnosis / Q000601:surgery*; D014057:Tomography, X-Ray Computed