title: Trichilemmal cyst involving the skull base.
abstract: BACKGROUND
  Trichilemmal cyst (TC) a rare tumour originating from the outer root sheath of the hair follicle particularly in the scalp has never been reported to involve the skull base. Here a case of TC extensively involving the skull base is presented. The neuro-imaging, operative, and pathological features are described. Possible histogenesis is also discussed.
  
  
  METHODS
  The clinical, radiological, operative, and pathological features of a TC involving the temporal-infratemporal fossae, orbit, paranasal sinuses, and the clivus is described.
  
  
  RESULTS
  Multilocular cysts full of keratinized material were found. Histopathological findings were consistent with those for a typical cutaneous TC.
  
  
  CONCLUSIONS
  TC of the variety found in the skin may involve the skull base extensively where it shows the typical histopathological features.
authors.affiliation: Department of Neurosurgery, Ain Shams University, Cairo, Egypt. Khaledbahy@yahoo.com
authors.forename: K
authors.initials: K
authors.lastname: El-Bahy
authors.forename: E
authors.initials: E
authors.lastname: Ishak
mesh_terms: D000368:Aged; D018859:Hair Follicle; D006801:Humans; D008297:Male; D018295:Neoplasms, Basal Cell / Q000473:pathology* / Q000601:surgery; D019292:Skull Base Neoplasms / Q000473:pathology* / Q000601:surgery