Mandible / maxilla
Odontogenic cysts
Keratocystic odontogenic tumor




Topic Completed: 1 December 2013

Revised: 8 February 2019

Copyright: 2004-2018, PathologyOutlines.com, Inc.

PubMed Search: Keratocystic odontogenic tumor [title]
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Cite this page: Morrison A. Odontogenic cysts: keratocystic odontogenic tumor. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/mandiblemaxillakeratocyst.html. Accessed February 18th, 2019.
Definition / general
  • Parakeratin lined cyst-like lesion / tumor within bone
Terminology
  • Formerly called odontogenic keratocyst (OKC), but reclassified as keratocystic odontogenic tumor (KCOT) due to its potential for aggressive behavior, recurrence and genetic abnormalities
  • The orthokeratinizing odontogenic cyst is considered an unrelated entity without risk of recurrence or aggressive growth or association with Nevoid basal cell carcinoma syndrome
Epidemiology
  • 4 - 12% of all odontogenic cysts (often compared to odontogenic cysts even though WHO classifies as tumor)
  • Peaks in second and third decade of life, but can occur over wide age range
  • 90% are solitary
  • Multiple tumors seen in Nevoid Basal Cell Carcinoma Syndrome / Gorlin Syndrome
Sites
  • Mandible most commonly involved (65 - 85% of KCOT)
  • Most common site: posterior mandible
  • Not uncommonly, but not exclusively associated with impacted teeth
  • Rarely occurs in soft tissue
Pathophysiology
  • Thought to arise from dental lamina
  • Two-hit mechanism results in bi-allelic loss of PTCH ("patched") tumor suppressor on 9q22.3-q31 causing dysregulation of p53 and cyclin D1 oncoproteins
  • Can occur sporadically or associated with Nevoid Basal Cell Carcinoma Syndrome / Gorlin Syndrome
Clinical features
  • Often asymptomatic, incidentally discovered on Xray
  • Can cause symptomatic swelling
  • Symptoms of pain and drainage if secondarily infected
  • Can cause local bone and soft tissue destruction, but usually spares teeth and roots
Diagnosis
  • Dependent on radiographic and histopathologic findings
Radiology description
  • Small lesions often unilocular radiolucent lesion, variable sclerotic margins
  • Larger lesions often multilocular, variable scalloped margins
Radiology images

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Odontogenic tumor in mandible

Prognostic factors
  • Recurrence rates of 20% to 56% with enucleation alone
  • Resection is widely reported to have no recurrences, but may be considered excessive for a benign entity
  • Multiple lesions can occur when associated with Gorlin Syndrome / Nevoid Basal Cell Carcinoma Syndrome
Case reports
  • 74 year old man with a keratocyst in the buccal mucosa with the features of keratocystic odontogenic tumor (Open Dent J 2013;7:152)
  • Synchronous occurrence of odontogenic myxoma with multiple keratocystic odontogenic tumors in nevoid basal cell carcinoma syndrome (J Craniofac Surg 2013;24:1840)
Treatment
  • Decompression alone
  • Enucleation with possible curettage
  • Chemical curettage with Carnoy’s solution
  • Marsupialization
  • Resection
  • Treatment must balance minimizing recurrence rate with morbidity associated with an extensive resection
Clinical images

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Well circumscribed mass

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Intraoral finding

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Less common maxillary lesion

Gross description
  • Thin fibrous wall; usually collapsed; clear fluid or keratinaceous debris if intact
  • Unerupted tooth
Gross images

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Cystic with thin smooth wall

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Massive KCOT

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Impacted maxillary third molar

Microscopic (histologic) description
  • Uniform epithelial lining 6 - 8 cells thick lacking rete ridges
  • May have artifactual clefting between epithelium and underlying fibroconnective tissue
  • Epithelium characterized by palisaded hyperchromatic basal cell layer comprised of cuboidal to columnar cells
  • May have areas of budding growth from the basal cells
  • Luminal surface has wavy ("corrugated") parakeratotic epithelial cells
  • Lumen may contain keratinaceous debris
  • Orthokeratinized variant: orthokeratosis (anuclear keratin), granular layer and poorly organized basal layer; not syndrome associated, less aggressive behavior
Microscopic (histologic) images

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Various images

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Classic features, budding, daughter cyst


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Low power

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Parakeratinized squamous cells

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Immunostains

Videos



Differential diagnosis