Odontogenic Keratocyst (OKC)

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The age of the patient, the location, and the apparent perforation of the bone all support a diagnosis of odontogenic keratocyst (OKC). For that reason, OKC should be placed high on the differential diagnosis list. However, the described expansion of the bone is unlike the typical behavior of an OKC, which hollows bone rather than causing it to expand. Nonetheless, the histology is supportive of an OKC.

Odontogenic keratocyst is an aggressive cyst known for its rapid growth and its tendency to invade the adjacent tissues, including bone. It has a high recurrence rate and is associated with bifid rib basal cell nevus syndrome. The majority of patients are in the age ranges of 20-29 and 40-59, but cases in patients ranging in age from 5 to 80 years have been reported. The distribution between sexes varies from equal distribution to a male-to-female ratio of 1.6:1, except in children. Odontogenic keratocyst predominantly affects Caucasian populations and, if one may judge from the limited evidence provided by the literature, is chiefly of Northern European descent.

Odontogenic keratocysts may occur in any part of the upper and lower jaw, with the majority (almost 70%) occurring in the mandible. They occur most commonly in the angle of the mandible and ramus. Posterior mandible is an area common to many benign odontogenic tumors such as ameloblastoma and odontogenic myxoma and is also a typical location for dentigerous cysts. Radiographically, OKCs present predominantly as unilocular radiolucencies with well-defined, sclerotic or scalloped borders. They may also present as multilocular radiolucencies. Odontogenic keratocysts of the maxilla are smaller in size when compared to those occurring in the mandible; larger OKCs tend to expand bone, but mildly—obvious clinical expansion (which is the case in this patient) should be viewed with suspicion for a neoplasm. OKCs can also present as small and oval radiolucencies between teeth simulating a lateral periodontal cyst, in an area of an extracted tooth simulating a residual cyst, at the apex of a vital tooth mistaken for a periapical cyst, or in the anterior maxilla between the central incisors simulating an incisive canal cyst. OKCs grow to sizes larger than any other odontogenic cysts. They usually penetrate the bone rather than expand it and grow in an anterior to posterior direction. Despite this aggressive growth, they often remain asymptomatic, thus growing to large sizes and hollowing the bone.

Odontogenic keratocysts are significant clinical entities due to their tendency for recurrence and destructive behavior. They are known to have a high recurrence rate, ranging from 13% to 60% (1, 2). Complete surgical removal is the treatment of choice. Surgery includes enucleation, curettage, enucleation with peripheral ostectomy, and resection depending on the radiographic presentation, location and clinical behavior. Surgery combined with Carnoy's solution or liquid nitrogen treatment has been effective in reducing the recurrence rate. At times, adjacent or associated teeth are extracted in the interest of complete removal. Some investigators advocate marsupialization and occasionally resection of the more aggressive cysts that tend to perforate buccal and lingual bone. Resection is a rare modality of treatment. Most cysts recur within the first three years while others may recur as late as after 16 years. Conservative surgical removal and long-term follow-up is the treatment of choice by most clinicians.