Odontogenic keratocyst

An odontogenic keratocyst (OKC) is a type of developmental cyst involving the mandible or maxilla. 

Epidemiology

Odontogenic keratocysts typically present in younger patients (2^nd - 3^rd decades), are often multiple, and may be seen in either the body or ramus of the mandible (approximately 70% of all OKCs), or maxilla. There may be male predilection.

Pathology

OKCs originate from epithelial cell rests (stratified squamous keratinizing epithelium) found along the dental lamina and periodontal margin of the alveolus of the mandible.

Associations

• basal cell naevus syndrome (or Gorlin-Goltz syndrome) : strong association.
• Marfan syndrome
• Noonan syndrome

Radiographic features

Plain film (OPG)

Typically seen as a solitary, lucent, unilocular lesion with smooth, corticated borders ⁵.  When in the mandible, they typically grow along the length of the bone.  In the maxilla, OKCs may expand into the maxillary sinus (as in Case 2).

They are often associated with an impacted tooth, mimicking a dentigerous cyst.  OKCs may occasionally appear septated, making the distinction from ameloblastoma difficult. The presence of multiple OKCs is associated with Gorlin-Goltz syndrome.

MRI

An OKC will typically demonstrate  ³

• T1 : low signal
• T2 : high signal 

Treatment and prognosis

They are locally aggressive. Treatment is often with enucleation / excision + / -aggressive curettage. They however can have a very high recurrence rate (30 - 60%)

Differential diagnoses

• dentigerous cyst if pericoronal
• ameloblastoma 
• calcifying odontogenic cyst (Gorlin cyst) and other odontogenic cysts and tumours

See also

• mandibular lesions
• WHO classification scheme for odontogenic tumours (1992)