Orthokeratinized Odontogenic cyst VS Odontogenic keratocyst - Histopathology
Orthokeratinized odontogenic cyst (OOC) was first described as an orthokeratinizing variant of odontogenic keratocyst (OKC) in 1981. It is now known and accepted that OOC is a distinct clinic-pathologic entity on its own. In fact it has been listed as a developmental odontogenic cyst in the recent WHO classification of odontogenic cysts.
Though OOC and OKC are keratinizing cysts, there are differences that help distinguish the two cysts. Lets have a look at the differences under the microscope.
The epithelial lining in OOC is orthokeratinized stratified squamous and has onion-skin like luminal keratinization. This is in contrast to OKC which has a parakeratinized lining.
OOC has a granular layer with prominent keratohyaline granules. OKC does not have a prominent granular layer.
OOC has cuboidal to flat basal cells with no nuclear palisading or reverse polarization. On the other hand, OKC has cuboidal to columnar basal cells with nuclei oriented away from the basement membrane.