Orthokeratinized odontogenic cyst: Report of eight cases and review of literature regarding its malignant transformation.

Orthokeratinized odontogenic cyst (OOC) is an uncommon odontogenic cyst. It has been categorized as a subtype of odontogenic keratocyst (OKC). In 2005, it was classified as a distinct entity. OOC should be histopathologically differentiated from OKC, which has a higher recurrence rate and lower malignant potential. In addition, OOC should be examined for malignant transformation. The epithelium of odontogenic cysts may rarely show malignant transformation. However, malignant transformation has been reported in inflammatory cysts such as the residual cyst and periapical cyst. The number of carcinomas arising from an OOC is low. This paper describes eight cases of OOC; out of which, two showed the development of squamous cell carcinoma from their epithelial lining.