title: Giant cell tumors of the clivus: Case report and literature review.
abstract: BACKGROUND
  Clival giant cell tumors (GCTs) are extremely rare with only eight cases reported to date, and malignant transformation is quite rare. Herein, we report a case of an uncontrolled clival GCT, which was transformed malignant, and review the literature.
  
  
  METHODS
  A 25-year-old man experienced double vision for 1 month. Computed tomography and magnetic resonance imaging revealed a clival tumor. The endonasal endoscopic transsphenoidal approach (EEA) was used, and partial resection was performed because of massive bleeding. Histological examination showed a GCT. After radiation therapy, the tumor recurred; the EEA and the anterior transpetrosal approaches were used to perform second and third operations, respectively. The MIB-1 index increased from 4.2% to 26.3%.
  
  
  CONCLUSIONS
  GCTs are difficult to treat because of their location, vascularity, and the potential for malignant transformation.
authors.affiliation: Department of Neurosurgery, Keio University School of Medicine, Tokyo 160-8582, Japan.
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Shibao
authors.affiliation: Department of Neurosurgery, Keio University School of Medicine, Tokyo 160-8582, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Toda
authors.affiliation: Department of Neurosurgery, Keio University School of Medicine, Tokyo 160-8582, Japan.
authors.forename: Kazunari
authors.initials: K
authors.lastname: Yoshida
keywords: Clivus; giant cell tumor; malignant transformation