odontogenic keratocyst |okc|

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oral pathololgy#odontogeniccyst#cyst#okc #odontogenickeratocyst
An odontogenic keratocyst is a rare and benign but locally aggressive developmental cyst. It most often affects the posterior mandible and most commonly presents in the third decade of life. Odontogenic keratocysts make up around 19% of jaw cysts.
In the WHO/IARC classification of head and neck pathology, this clinical entity had been known for years as the odontogenic keratocyst; it was reclassified as keratocystic odontogenic tumour (KCOT) from 2005 to 2017. In 2017 it reverted to the earlier name, as the new WHO/IARC classification reclassified OKC back into the cystic category. Under The WHO/IARC classification, Odontogenic Keratocyst underwent the reclassification as it is no longer considered a neoplasm due to a lack of quality evidence regarding this hypothesis, especially with respect to clonality. Within the Head and Neck pathology community there is still controversy surrounding the reclassification, with some pathologists still considering Odontogenic Keratocyst as a neoplasm in line with the previous classificationOdontogenic 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.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 mutationRadiographs of odontogenic keratocysts show well-defined radiolucent areas with rounded or scalloped margins which are well demarcated.These areas can be multilocular or unilocular. The growth pattern of the lesion is very characteristic from which a diagnosis can be made as there is growth and spread both forward and backward along the medullary cavity with little expansion. No resorption of teeth or inferior dental canal and minimal displacement of teeth is seen. Due to lack of expansion of the odontogenic keratocyst, the lesion can be very large when radiographically discovered.Radiologically
Odontogenic myxomaAmeloblastomaCentral giantcellgranulomaAdenomatoid odontogenic tumorDentigerous cyst (follicular cyst)
Histologically
Orthokeratocyst
Radicular cyst (particularly if the OKC is very inflamed)
Ameloblastoma
Histology
Odontogenic keratocysts have a diagnostic histological appearance. Under the microscope, OKCs vaguely resemble keratinized squamous epithelium; however, they lack rete ridges and often have an artifactual separation from their basement membrane.
The fibrous wall of the cyst is usually thin and uninflamed. The epithelial lining is thin with even thickness and parakeratinised with columnar cells in the basal layer which have focal reverse polarisation (nuclei are on the opposite pole of the cell).The basal cells are an indication of the odontogenic origin as they resemble pre-ameloblasts. The epithelium can separate from the wall, resulting in islands of epithelium. These can go on to form 'satellite' or 'daughter' cysts, leading to an overall multilocular cyst. Presence of daughter cysts is particularly seen in those with NBCCS. Inflamed cysts show hyperplastic epithelium which is no longer characteristic of OKCs and can have resemblance to radicular cysts instead. Due to areas of focal inflammation, a larger biopsy is required for correct diagnosis of odontogenic keratocysts.Treatment options:
Surgical enucleation: surgical removal of the entire epithelial lining of the cyst.
Marsupialisation followed by enucleation: this method is carried out by surgeons for larger cysts.
Curettage involving simple excision and scraping-out of cavity.
Carnoy's solution fixative (ethanol, chloroform and acetic acid) which is usually used in conjunction with excision and curretage. 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
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  Nevoid Basal Cell Carcinoma Syndrome