title: Diagnostic dilemma of unicystic ameloblastoma: novel parameters to differentiate unicystic ameloblastoma from common odontogenic cysts.
abstract: OBJECTIVE
  Diagnostic criteria that have been specified for unicystic ameloblastomas (UAs) are not always helpful to differentiate these cystic tumors from common odontogenic cysts. The aim of this study therefore was to identify additional histopathological features (other than the features considered for the diagnosis of UA at present) that would be helpful to differentiate UA from odontogenic cysts.
  
  
  METHODS
  One hundred histopathologically confirmed unicystic ameloblastomas and 20 cases each of radicular, inflamed dentigerous and non-inflamed dentigerous cysts were selected. Histopathological features of the UAs that are not used as diagnostic criteria at present were identified.
  
  
  RESULTS
  Hyperplastic arcading epithelial proliferations with stellate-reticulum-like and vacuolated cells were always seen associated with inflammation in odontogenic cysts, while in UA plexiform-like areas were also seen without inflammation (P < 0.001). In addition, a spiky rete pattern was observed in non-inflamed UA while this pattern was observed only in inflamed odontogenic cysts. Furthermore, spiky retes together with subepithelial hyalinization were usually observed in UAs while only subepithelial hyalinization was observed in non-inflamed dentigerous cysts.
  
  
  CONCLUSIONS
  Combinations of histopathological features were identified to differentiate non-inflamed UA from common odontogenic cysts. However, presence of inflammatory changes in UA precludes the use of features identified in the present study for diagnostic purposes.
authors.affiliation: Department of Oral Pathology, Faculty of Dental Sciences, University of Peradeniya, Kandy, Sri Lanka.
authors.forename: Kuda Singappulige Niluka Darshani
authors.initials: KS
authors.lastname: Gunawardhana
authors.forename: Primali Rukmal
authors.initials: PR
authors.lastname: Jayasooriya
authors.forename: Wanninayake Mudiyanselage
authors.initials: WM
authors.lastname: Tilakaratne
mesh_terms: D000564:Ameloblastoma / Q000175:diagnosis* / Q000473:pathology; D000565:Ameloblasts / Q000473:pathology; D003238:Connective Tissue / Q000473:pathology; D003803:Dentigerous Cyst / Q000175:diagnosis* / Q000473:pathology; D003937:Diagnosis, Differential; D004847:Epithelial Cells / Q000473:pathology; D004848:Epithelium / Q000473:pathology; D005260:Female; D006801:Humans; D006818:Hyalin / Q000737:chemistry; D006965:Hyperplasia; D007249:Inflammation / Q000473:pathology; D007633:Keratins / Q000032:analysis; D008297:Male; D011842:Radicular Cyst / Q000175:diagnosis* / Q000473:pathology; D014617:Vacuoles / Q000648:ultrastructure; D055815:Young Adult
chemical_list: D007633:Keratins
keywords: dentigerous cyst; differential diagnosis; histopathology; odontogenic cysts; unicystic ameloblastomas