title: Spinal arachnoid cyst containing nevus cells in a patient with a large congenital melanocytic nevus: case report.
abstract: OBJECTIVE
  Spinal arachnoid cysts are rare, and their cause and pathogenesis remain controversial. We experienced a rare case with a large congenital melanocytic nevus in which a spinal arachnoid cyst contained nevus cells, suggesting the congenital nature of a spinal arachnoid cyst.
  
  
  METHODS
  A 37-year-old Japanese man had been born with a large melanocytic nevus on his back. He experienced intermittent pain radiating to both thighs and to the lower back and waist. A magnetic resonance imaging study disclosed the presence of a posterior intradural extramedullary arachnoid cyst extending from T10 through T12. His spinal cord was displaced anteriorly and flattened.
  
  
  METHODS
  An osteoplastic laminoplasty was performed, and the arachnoid cyst was totally removed. The cyst membrane exhibited many foci of brown deposits, and histological examination disclosed the presence of melanin-containing cells in the cyst membrane. Morphologically and immunohistochemically, the melanin-containing cells in the cyst membrane were similar to nevus cells in the dermis.
  
  
  CONCLUSIONS
  The histological findings of our case suggest that the patient's spinal arachnoid cyst was formed at the same stage of development as the melanocytic nevus.
authors.affiliation: Department of Neurosurgery, Kumamoto University School of Medicine, Kumamoto, Japan. morioka@kaiju.medic.kumamoto-u.ac.jp
authors.forename: Motohiro
authors.initials: M
authors.lastname: Morioka
authors.forename: Jun-ichiro
authors.initials: J
authors.lastname: Hamada
authors.forename: Yuki
authors.initials: Y
authors.lastname: Ohmori
authors.forename: Toshiro
authors.initials: T
authors.lastname: Kageshita
authors.forename: Yukitaka
authors.initials: Y
authors.lastname: Ushio
mesh_terms: D000328:Adult; D016080:Arachnoid Cysts / Q000175:diagnosis*; D006801:Humans; D008297:Male; D009506:Nevus / Q000151:congenital* / Q000473:pathology*; D013125:Spinal Neoplasms / Q000151:congenital* / Q000473:pathology*