title: Long-term follow-up of a case of aneurysmal bone cyst in the lumbar spine.
abstract: BACKGROUND
  Aneurysmal bone cyst (ABC) in the spine is relatively rare, so little is known about the natural history of the disease.
  
  
  OBJECTIVE
  The purpose of this study was to describe a spinal ABC that was followed for an extended period from lesion enlargement to spontaneous regression.
  
  
  METHODS
  Case report.
  
  
  METHODS
  A 63-year-old woman had a 1-year-long history of mild low back and bilateral leg pain without any significant neurologic deficits caused by lumbar spinal stenosis. At her first visit to our hospital, magnetic resonance imaging (MRI) showed a small cystic lesion on the left side of the L5 vertebral body. The patient's clinical symptom progression and MRI and computed tomography evaluations were reported for >13 years.
  
  
  RESULTS
  After 6 years, the cystic lesion enlarged significantly and extended into the left pedicle and transverse process of the L5 vertebra. The lesion was diagnosed as an ABC based on multilocular cysts with fluid-fluid levels on MRI and bony septations on computed tomography. Thirteen years after the first visit, the lesion regressed spontaneously without a clear reason, such as biopsy or fracture, and most of the lesion was replaced by fatty marrow. The patient's symptoms stabilized without neurologic deterioration during the follow-up period.
  
  
  CONCLUSIONS
  Although spinal ABC is an expandable cystic lesion, we should consider that such a lesion in an elderly patient could spontaneously regress.
authors.affiliation: Department of Orthopaedic Surgery, Karatsu Red Cross Hospital, 1-5-1 Futago Karatsu, Saga 847-8588, Japan. Electronic address: kitataka0330@karatsu.jrc.or.jp.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Kitamura
authors.forename: Ko
authors.initials: K
authors.lastname: Ikuta
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Senba
authors.forename: Norihiro
authors.initials: N
authors.lastname: Komiya
authors.forename: Satoshi
authors.initials: S
authors.lastname: Shidahara
mesh_terms: D017824:Bone Cysts, Aneurysmal / Q000473:pathology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008159:Lumbar Vertebrae / Q000473:pathology*; D008875:Middle Aged; D012075:Remission, Spontaneous; D013122:Spinal Diseases / Q000473:pathology*
keywords: Aneurysmal bone cyst; Lumbar spine; Spontaneous regression