Case 1: A corrugated parakeratoic layer overlies the epithelial layer. Note the nicely pallisaded basal layer. An artifactual separation of epidermis from underlying fibrous connective tissue is common.
Odontogenic keratocysts (OKCs, aka keratocystic odontogenic tumor) are one of the more common developmental cysts of the jaw, representing 5-15% of all odontogenic cysts. It may arise sporadically or as part of the nevoid-basal cell carcinoma (Gorlin syndrome).
Gorlin syndrome has the following features: multiple basal cell carcinomas, multiple odontogenic keratocysts, medulloblastoma, calcified falx, palmar and plantar pits, and skeletal anomalies commonly in the bifid rib. The genetic lesion is an autosomal dominant inherited mutation in the PATCHED tumor suppressor gene. The mutated PTCH leads to ligand-independent signal transduction and unregulated cell division (tumors) as well as abnormal patterning (e.g. rib abnormalities).
Histological criteria include: (1) an epithelial lining that is 6-10 layers thick, usually without rete ridges; (2) a well-defined, palisading basal cell layer; (3) surface keratinization that is corrugated, refractile and parakeratotis; (4) and a fibrous connective tissue cyst wall that is thin and usually uninflamed. Often, the epithelium is separated from the fibrous wall.
Note that there is a variant that exhibits orthokeratosis instead of parakeratosis. This subtype, orthokeratinized odontogenic cyst, differs from the usual odontogenic keratocysts in that it does not have a palisading basal layer and as previously mentioned, has a orthokeratotic layer. This particular variant is not syndrome associated and has less aggressive behavior (Regezi).
Peak incidence is between the 2nd and 4th decade, but can occur in all ages. The mean age of patients with multiple odontogenic keratocysts (OKCs) is younger than those with single OKCs. Some studies show a male predilection while others show a female predilection (Greer). On imaging, a multilocular radiolucency is seen.
It can occur anywhere in the jaw (mandible or maxilla), although the posterior mandible is favored. The cyst can be located over the apices of teeth or adjacent to crowns of impacted teeth. They are often multilocular (Regezi).
The radiograph usually shows a well-defined radiolucent lesion that is either unilocular or multilocular, with smooth corticated margins, unless the lesion is infected.
Wide local excision or simple excision.
OKCs have potential for aggressive behavior and recurrence. Up to 30% of cases recur. Partial jaw resection may be necessary.
Greer RO, et al. Odontogenic Keratocysts: eMedicine. Last updated on Sept 11 2010. Available at: emedicine.medscape.com/article/1731868-overview
Regezi JA. Odontogenic Cysts, Odontogenic Tumors, Fibroosseous, and Giant Cell Lesions of the Jaws. Mod Pathol 2002;15(3):331-341.
Slootweg PJ. Lesions of the Jaw. Histopathology 2009, 54, 401-418.