Odontogenic keratocysts are usually noted as incidental radiographic findings. Radiographically they can be seen as unilocular or multilocular radiolucencies. They can be mistaken for other cysts such as residual cysts or a dentigerous cyst if they occur over an unerupted tooth. Pathogenesis
Odontogenic keratocysts originate from the odontogenic epithelium (dental lamina) in the alveolus left from tooth development stages. They are mainly thought to arise from rests of Serres. Genetics
Sporadic (non-syndromic) and syndromic OKCs are associated with mutations in the gene PTCH found on chromosome 9q, which is part of the Hedgehog signaling pathway. PTCH is a tumour suppressor gene. Loss of PTCH activity leads to a brake in the cell cycle. A third of OKCs show mutations in PTCH, resulting in the cyst epithelium undergoing highly proliferative activity. This leads to growth of the cyst wall and when removed favours recurrence if following incomplete removal of the epithelium. Nevoid basal-cell carcinoma syndrome
Multiple odontogenic keratocysts are a feature, and major diagnostic criteria, of nevoid basal cell carcinoma syndrome (NBCCS, also known as Gorlin-Goltz Syndrome). Almost all individuals with NBCCS have odontogenic keratocysts which require numerous treatments. Consideration of the syndrome needs to be taken into account if found in children or if multiple OKCs are present; diagnosis of multiple OKCs in a child necessitates referral for genetic evaluation. Histologically, the cysts are indistinguishable to non-syndromic cysts and over 80% will have PTCH mutations. Diagnosis
Diagnosis is usually radiological. However, definitive diagnosis is through biopsy.
Cavity wall can be treated with the fixative either before enucleation to kill the lining of the wall or added after curretage to bony walls, killing any residual epithelial cells to a depth of 1-2mm. Used with care near mandibular canal and the neurovascular bundle within. Marsupialization which involves the surgical opening of the cyst cavity and a creation of a marsupial-like pouch. This allows the cavity to be in contact with the outside of the cyst for an extended period of time. Marsupialisation results in slow shrinkage of the cyst allowing later enucleation. However, resolution can take up to 20 months and patients are required to clean the open cavity and irrigate it. Peripheral ostectomy after curettage and/or enucleation. Extensive cysts may require a bone graft after bone resection and reconstruction of the area. Simple excision
Enucleation and cryotherapy. Decompression followed by enucleation has been shown to be most successful with lowest recurrence rates. Topical application of 5FU after enucleation
Ostectomy or En – bloc resection: in addition to the above treatments, these may be required due to the issue of recurrence. Ostectomy is removal of peripheral bone. En – block resection is removal of the cyst with the surrounding tissue. Extensive cysts may require a bone graft after bone resection and reconstruction of the area. Follow-up
Annual radiographic review has been recommended. Long-term clinical follow-up is also recommended due to recurrences occurring many years after treatment. Recurrence and neoplastic nature
Malignant transformation to squamous cell carcinoma may occur, but is unusual.Recurrence is likely when treated by simple enucleation.