title: Reclassification of odontogenic keratocyst as tumour. Impact on the odontogenic tumours prevalence.
abstract: OBJECTIVE
  The aim of this study was to establish the impact of the redefinition and reclassification of odontogenic keratocyst (OKC) as a tumour on the prevalence of odontogenic tumours (OT).
  
  
  METHODS
  We revised 15 435 files of a teaching head and neck histopathology service in the time period from January 1981 to December 2008 and 478 cases of OT were selected. The 342 cases from 1981 to 2004 were classified according 1992 to the World Health Organization (WHO)-classification (excluding keratocystic OT) while the 136 cases from 2005 onwards were classified according to the 2005 WHO-classification (including keratocystic OT). Age and gender were obtained from medical records. The frequency distribution and prevalence of OT from each periods of time were compared. A chi-square test was performed (P < 0.05 95% confidence interval).
  
  
  RESULTS
  The prevalence of OT increases 92% in the 2005-2008 period; from 2.6% (1981-2004 period) to 5% (2005-2008 period) (P 0.000).The most frequent OT in the 1981-2004 period was odontoma (45% of all OT) while in the 2005-2008 period was Keratocystic Odontogenicv Tumour (38.9%).
  
  
  CONCLUSIONS
  The redefinition of OKC as a tumour produced an increase in the frequency and prevalence of OT.
authors.affiliation: Oral Pathology Laboratory, Dental School, National Autonomous University of México, México City, México. lgaitan@servidor.unam.mx
authors.forename: L A
authors.initials: LA
authors.lastname: Gaitán-Cepeda
authors.forename: D
authors.initials: D
authors.lastname: Quezada-Rivera
authors.forename: F
authors.initials: F
authors.lastname: Tenorio-Rocha
authors.forename: E R
authors.initials: ER
authors.lastname: Leyva-Huerta
mesh_terms: D000367:Age Factors; D000564:Ameloblastoma / Q000453:epidemiology; D001706:Biopsy; D003803:Dentigerous Cyst / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D008800:Mexico / Q000453:epidemiology; D009807:Odontogenic Cysts / Q000145:classification* / Q000453:epidemiology / Q000473:pathology; D009808:Odontogenic Tumors / Q000145:classification* / Q000453:epidemiology / Q000473:pathology; D009810:Odontoma / Q000453:epidemiology; D015995:Prevalence; D011842:Radicular Cyst / Q000453:epidemiology; D012189:Retrospective Studies; D012737:Sex Factors; D014944:World Health Organization