Odontogenic Keratocyst
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- Benign but aggressive intraosseous lesions of odontogenic origin
- Reclassified back to odontogenic keratocyst in the WHO 2017 classification (previously classified as keratocystic odontogenic tumour [KCOT] from 2005 to 2017)[1]
- Subtypes:
- Odontogenic Keratocyst (OKC) - parakeratinised
- Orthokeratinised Odontogenic Keratocyst (OOKC)
Epidemiology[edit | edit source]
- Account for 5-10% of jaw cysts
- Peak incidence 20-30yrs
- ♂ > ♀ (slightly)
- Commonest site — angle of the mandible
- 70-80% occur in the mandible
- 50% at the angle of the mandible
Clinical Features[edit | edit source]
- Usually asymptomatic (commonly incidental findings)
- When large/infected can cause pain/swelling/discharge/pathological fracture/tooth displacement/buccal expansion
- Characteristic insidious pattern of growth
- Unlike other cysts, OKCs do not have a high internal pressure ∴ they preferentially expand along the medullary cavity (the path of least resistance)
- A cyst in the mandible may extend through much of the ramus and body without significant expansion of the jaw
- Clinical signs often fail to appear until the cyst is well advanced
- Usually solitary cysts (consider Nevoid basal-cell carcinoma syndrome (Gorlin-Goltz Syndrome))
- High recurrence rate
Differential Diagnosis[edit | edit source]
Memory Aid - Multilocular lesions of the mandible (MACHO) |
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- Other cysts of the jaws
- Radiological differentials:
- Odontogenic myxoma
- Ameloblastoma
- Central giant-cell granuloma
- Haemangioma/Vascular malformations
- Adenomatoid odontogenic tumor
- Dentigerous cyst
- Histological differentials:
Aetiology and Pathogenesis[edit | edit source]
Aetiology[edit | edit source]
- Developmental cyst - arises from dental lamina and its remnants (cell rests of Serres)
- Can be sporadic or syndromic
- Syndromic cases:
- Associated with mutation/inactivation of PTCH gene (which activates SHH pathway)
- 5% occur as part of Nevoid basal-cell carcinoma syndrome (Gorlin-Goltz Syndrome)
Pathogenesis[edit | edit source]
- Mutation of PTCH
- PTCH is a tumour suppressor gene that encodes the PTCH protein
- PTCH protein is a receptor for sonic hedgehog (SHH)
- In adult tissue, SHH plays a role in cell cycle regulation (SHH dysfunction is implicated in various cancer types)
- ↓ PTCH gene activity → release of the break on cell cycle (mediated by SHH) → ↑ proliferative activity in epithelial lining of keratocysts
- This increase in proliferative activity causes enlargement of the cyst by mural growth (as opposed to osmotic growth seen in other cysts)
- Increase in proliferative activity may also contribute to recurrence rates
- Mural growth of cysts
- Growth is by extension of finger-like processes into marrow spaces rather than by expansion (growth is said to be "neoplastic")
- Growth of the wall is faster than the expansion of cyst cavity ∴ the lining becomes folded
- Cyst enlarges slowly along the pathway of least resistance
Investigations[edit | edit source]
Laboratory Investigations[edit | edit source]
Aspiration of cyst contents may be helpful for analysis of protein content (biochemistry) and keratinization (cytology)
Imaging[edit | edit source]
Plain film[edit | edit source]
- Well defined radiolucent area with a sharply demarcated and corticated bony wall
- Radiographically usually multilocular
- Unilocular lesions tend to have a scalloped margin
- When multilocular, can mimic ameloblastoma if many locules exist
- Can mimic other cysts
- 40% in a ‘dentigerous’ position
- Adjacent roots/teeth may become displaced by large cysts, but usually the cyst will extend around the roots and inferior alveolar nerve without displacing them or causing significant expansion
Computed Tomography[edit | edit source]
- Can facilitate diagnosis, and 3D characterisation for surgical planning
Histopathology[edit | edit source]
- Biopsy is the diagnostic investigation of choice (OKCs have a consistent and unique appearance)
- Features:
- Epithelium
- Regular stratified squamous epithelium
- 5-8 cells thick
- Palisaded basal layer (cells are columnar in shape)
- Lack rete ridges
- Often have artifactual separation from basement membrane
- Corrugated surface which can be parakeratinized (83%), orthokeratinized (10%) or both (7%)
- Thin fibrous capsule
- Satellite (daughter) cells
- Particularly seen in those with NBCCS
- Cyst contents
- Fluid has protein content <4g/ dL
- High mitotic activity
- Inflammatory changes
- Inflamed cysts show hyperplastic epithelium which is no longer characteristic of OKCs and can have resemblance to radicular cysts instead
- A larger biopsy is needed to confirm OKC if there is inflammation
- Epithelium
Management[edit | edit source]
- !Controversial topic¡
- Diagnosis must be confirmed by biopsy
- Treatment considerations:
Unilocular + small multilocular lesions[edit | edit source]
- Conservative enucleation and bone curettage
- Difficult to ensure all of cyst lining is removed ∵ friable capsule + complex outline of cyst
- Epithelial remnants and satellite/daughter cysts can easily be left behind after enucleation
- It is currently considered that enucleation alone is an inadequate form of treatment and needs to be used in combination with adjuvant methods (see below)
Large cyst extending around muti-rooted teeth[edit | edit source]
- Difficult to completely remove, teeth may have to be sacrificed to ensure complete removal
- May require decompression first followed by enucleation
- Decompression is a modified marsupialization technique which causes the cyst to decrease significantly in size and the cystic lining becomes thicker resembling oral mucosa that allows for easier enucleation
- This method decreases the levels of IL-1α which regulates epithelial cell proliferation in OKC; hence, there is immune-histochemical evidence that decompression is superior to enucleation alone
Very large cyst[edit | edit source]
- Resection and bone reconstruction (free-flap)
- Resection provides the least recurrences
Adjuvant treatment to enucleation[edit | edit source]
- Peripheral ostectomy
- Aggressive form of adjuvant therapy where methylene blue is utilised to stain any cystic remnants and a rosehead bur is used to remove these
- Carnoy's solution
- Chemical curettage that causes cell necrosis of the cystic lining
- Cryotherapy (liquid nitrogen)
- Liquid nitrogen causes cell necrosis of the cystic lining
Suggested Management Protocol[edit | edit source]
Prognosis and Complications[edit | edit source]
- Recurrence:
- High recurrence rate (up to 60%)
- Higher in NBCCS and presence of satellite cells
- Lower in orthokeratinised odontogenic keratocysts
Study | Enucleation alone | Enucleation & Peri-oestectomy | Enucleation & Carnoy’s solution | Enucleation & cryotherapy | Marsupialization/ decompression alone | Decompression & residual cystectomy | Resection |
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Al-Moraissi et al. (2017)[3] | 23.10 | 17.40 | 11.50 | 14.50 | 32.30 | 14.60 | 8.40 |
de Castro et al. (2018)[4] | 20.80 | NA | NA | NA | 18.50 | 11.90 | NA |
Chrcanovic and Gomez (2017)[5] | 22.50 | 18.60 | 5.30 | 20.90 | 28.70 | 18.60 | 2.20 |
Johnson et al. (2013)[6] | 25.60 | NA | 7.90 | 30.30 | NA | 15.80 | 6.30 |
Kaczmarzyk et al. (2012)[7] | 26.09 | 18.18 | 50 | NA | 40 | NA | 0 |
Average | 23.60 | 18.10 | 18.70 | 21.90 | 29.90 | 15.20 | 4.20 |
Follow-up[edit | edit source]
- Yearly follow-up for at least 5 years
- Orthopantogram every year, MRI every 2 years
References[edit | edit source]
- ↑ El-Naggar AK, Chan JK, Grandis JR. WHO classification of head and neck tumours. 2017. ISBN: 9789283224389
- ↑ Titinchi F. Protocol for management of odontogenic keratocysts considering recurrence according to treatment methods. Journal of the Korean Association of Oral and Maxillofacial Surgeons. 2020 Oct 31;46(5):358-60.
- ↑ Al-Moraissi EA, Dahan AA, Alwadeai MS, Oginni FO, Al-Jamali JM, Alkhutari AS, Al-Tairi NH, Almaweri AA, Al-Sanabani JS. What surgical treatment has the lowest recurrence rate following the management of keratocystic odontogenic tumor?: A large systematic review and meta-analysis. Journal of Cranio-Maxillofacial Surgery. 2017 Jan 1;45(1):131-44.
- ↑ [Castro MS, Caixeta CA, de Carli ML, Júnior NV, Miyazawa M, Pereira AA, Sperandio FF, Hanemann JA. Conservative surgical treatments for nonsyndromic odontogenic keratocysts: a systematic review and meta-analysis. Clinical oral investigations. 2018 Jun;22(5):2089-101.]
- ↑ Chrcanovic BR, Gomez RS. Recurrence probability for keratocystic odontogenic tumors: an analysis of 6427 cases. Journal of Cranio-Maxillofacial Surgery. 2017 Feb 1;45(2):244-51.
- ↑ Johnson NR, Batstone MD, Savage NW. Management and recurrence of keratocystic odontogenic tumor: a systematic review. Oral surgery, oral medicine, oral pathology and oral radiology. 2013 Oct 1;116(4):e271-6.
- ↑ Kaczmarzyk T, Mojsa I, Stypulkowska J. A systematic review of the recurrence rate for keratocystic odontogenic tumour in relation to treatment modalities. International journal of oral and maxillofacial surgery. 2012 Jun 1;41(6):756-67.