Histology and ultrastructural features of the odontogenic keratocyst

Abstract

In comparison to other cysts of the jaws, the odontogenic keratocyst (OKC) is unusual because it shows characteristic clinical features, including potentially aggressive behavior, high recurrence rate, and an association with the nevoid basal cell carcinoma syndrome. The defining histologic feature—the presence of parakeratin—is unique among the myriad inflammatory and developmental cysts that occur in the jaws. The presence of keratin coupled with other characteristic histologic findings is so distinctive that microscopic diagnosis is usually obvious. At outset, it is important to define two specific entities under discussion. Histologically, the OKC is composed of parakeratinized stratified squamous epithelium but may rarely show foci of orthokeratinization. This cyst occurs sporadically or may be associated with the nevoid basal cell carcinoma syndrome. By contrast, the orthokeratinized odontogenic cyst (OOC), as the name implies, is composed exclusively of epithelium that shows orthokeratinization. Although initially believed to be a subtype of OKC, it is established that it has clinical, histologic, and biologic features that set it apart from the OKC. This cyst does not occur in association with the nevoid basal cell carcinoma syndrome. This article will review the histological and ultrastructural features of the OKC and the OOC.