Keratocystic odontogenic tumour

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Odontogenic keratocyst
Keratocystic odontogenic tumour - 2 - very high mag.jpg
Micrograph of an odontogenic keratocyst. H&E stain.
Classification and external resources
ICD-10 D16.4 (Maxilla); D16.5 (mandible)
ICD-9-CM 213.0-213.1

An odontogenic keratocyst is a rare and benign but locally aggressive developmental cyst. It most often affects the posterior mandible. It most commonly presents in the third decade of life.[1]

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.[2][3] In 2017 it reverted to the earlier name, as the new WHO/IARC classification reclassified OKC back into the cystic category.[4] The WHO/IARC classification no longer considers it a neoplasm, because the evidence supporting that hypothesis (for example, clonality) is considered insufficient. However, this is an area of hot debate within the head and neck pathology community, and some pathologists still regard OKC as a neoplasm despite the reclassification.

Signs and symptoms[edit]

Swelling is the most common presenting complaint; however, OKCs may be asymptomatic and found incidentally on dental X-rays.[5]

Cancer[edit]

Malignant transformation to squamous cell carcinoma may occur, but is unusual.[6]

Cause[edit]

KCOTs are thought to arise from the dental lamina and are associated with impacted teeth. Multiple odontogenic keratocysts are a feature of nevoid basal cell carcinoma syndrome. Odotogenic Keratocysts are derived from the remnants of the Dental Lamina.

Genetics[edit]

Sporadic (non-syndromic) and syndromic KCOTs are associated with mutations in the gene PTCH, which is part of the Hedgehog signaling pathway.[3][7]

Diagnosis[edit]

Classic look to a keratocyctic odontogenic tumor in the right mandible in the place of a former wisdom tooth. Unicystic lesion growing along the bone.

The definitive diagnosis is by histologic analysis, i.e. excision and examination under the microscope.

Under the microscope, OKCs vaguely resemble keratinized squamous epithelium;[8] however, they lack rete ridges and often have an artifactual separation from their basement membrane.

On a CT scan, The radiodensity of a keratocystic odontogenic tumour is about 30 Hounsfield units, which is about the same as amelioblastomas. Yet, amelioblastomas show more bone expansion and seldom show high density areas.[9]

Differential diagnosis[edit]

Radiologically

Histologically

  • Orthokeratocyst
  • Radicular cyst (particularly if the OKC is very inflamed)
  • Unicystic ameloblastoma

Treatment[edit]

Massive keratocystic odontogenic tumour with impacted wisdom teeth superficial to lesion

As the condition is quite rare, opinions among experts about how to treat OKCs differ.

Treatment options:[3]

  • Wide (local) surgical excision.
  • Marsupialization - the surgical opening of the (OKC) cavity and a creation of a marsupial-like pouch, so that the cavity is in contact with the outside for an extended period, e.g. three months.
  • Curettage (simple excision & scrape-out of cavity).
  • Peripheral ostectomy after curettage and/or enucleation.
  • Simple excision.
  • Carnoy's solution - usually used in conjunction with excision.
  • Enucleation and cryotherapy [10]

References[edit]

  1. ^ MacDonald-Jankowski, D S (2011). "Keratocystic odontogenic tumour: systematic review". Dentomaxillofacial Radiology. 40 (1): 1–23. ISSN 0250-832X. doi:10.1259/dmfr/29949053. 
  2. ^ Barnes, L; Eveson, JW; Reichart, P; Sidransky, D, eds. (2005), World Health Organization Classification of Tumours: Pathology and Genetics of Head and Neck Tumours (PDF), World Health Organization Classification of Tumours (2005 ed.), Lyon, France: IARC Press, ISBN 978-92-832-2417-4. 
  3. ^ a b c Madras, J; Lapointe, H (2008). "Keratocystic odontogenic tumour: reclassification of the odontogenic keratocyst from cyst to tumour". J Can Dent Assoc. 74 (2): 165–165h. PMID 18353202. 
  4. ^ El-Naggar, Adel K; Chan, John KC; Grandis, Jennifer R; Takata, Takashi; Slootweg, Pieter J, eds. (2017), WHO Classification of Head and Neck Tumours, WHO/IARC Classification of Tumours, 9 (4th ed.), Lyon, France: IARC Press, ISBN 978-92-832-2438-9. 
  5. ^ Habibi A, Saghravanian N, Habibi M, Mellati E, Habibi M (September 2007). "Keratocystic odontogenic tumor: a 10-year retrospective study of 83 cases in an Iranian population". J Oral Sci. 49 (3): 229–35. PMID 17928730. doi:10.2334/josnusd.49.229. [dead link]
  6. ^ Piloni MJ, Keszler A, Itoiz ME (2005). "Agnor as a marker of malignant transformation in odontogenic keratocysts". Acta Odontol Latinoam. 18 (1): 37–42. PMID 16302459. 
  7. ^ PATCHED, DROSOPHILA, HOMOLOG OF, 1; PTCH1. OMIM. URL: http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=601309. Accessed on: December 25, 2008.
  8. ^ Thompson LDR. Head and neck pathology - (Foundations in diagnostic pathology). Goldblum JR, Ed.. Churchill Livingstone. 2006. ISBN 0-443-06960-3.
  9. ^ Ariji, Y; Morita, M; Katsumata, A; Sugita, Y; Naitoh, M; Goto, M; Izumi, M; Kise, Y; Shimozato, K; Kurita, K; Maeda, H; Ariji, E (2011). "Imaging features contributing to the diagnosis of ameloblastomas and keratocystic odontogenic tumours: logistic regression analysis". Dentomaxillofacial Radiology. 40 (3): 133–140. ISSN 0250-832X. doi:10.1259/dmfr/24726112. 
  10. ^ Schmidt BL, Pogrel MA (2001). "The use of enucleation and liquid nitrogen cryotherapy in the management of odontogenic keratocysts.". J Oral Maxillofac Surg. 59: 720–727. doi:10.1053/joms.2001.24278. 

Additional reading[edit]

  • Kahn, Michael A. Basic Oral and Maxillofacial Pathology. Volume 1. 2001.