- 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]
- 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]
- 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]
Memory Aid - Multilocular lesions of the mandible (MACHO)
|
- Mxyoma
- Amelobastoma
- Central giant cell tumour
- Haemangioma/vascular malformation
- Odontogenic Keratocyst
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Aetiology and Pathogenesis[edit]
Aetiology[edit]
- Developmental cyst - arises from dental lamina and its remnants (cell rests of Serres)
- Can be sporadic or syndromic
- Syndromic cases:
Pathogenesis[edit]
- 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]
Unilocular odontogenic keratocyst
Large multilocular odontogenic keratocyst
Intermediate magnification of an odontogenic keratocyst showing a folded cyst.
High magnification of an odontogenic keratocyst.
Laboratory Investigations[edit]
Aspiration of cyst contents may be helpful for analysis of protein content (biochemistry) and keratinization (cytology)
Imaging[edit]
Plain film[edit]
- 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]
- Can facilitate diagnosis, and 3D characterisation for surgical planning
Histopathology[edit]
- 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
Management[edit]
- !Controversial topic¡
- Diagnosis must be confirmed by biopsy
- Treatment considerations:
Unilocular + small multilocular lesions[edit]
- 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]
- 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]
- Resection and bone reconstruction (free-flap)
- Resection provides the least recurrences
Adjuvant treatment to enucleation[edit]
- 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]
Management protocol for odontogenic keratocysts (OKC). (CT: computed tomography, MRI: magnetic resonance imaging, IAN: inferior alveolar nerve, Rx: treatment, RR: recurrence rates). Image from Titinchi 2020
Prognosis and Complications[edit]
- Recurrence:
- High recurrence rate (up to 60%)
- Higher in NBCCS and presence of satellite cells
- Lower in orthokeratinised odontogenic keratocysts
Summary of recurrence rates (%) for different surgical methods in the management of odontogenic keratocysts - data from 5 large systematic reviews[2]
Study |
Enucleation alone |
Enucleation & Peri-oestectomy |
Enucleation & Carnoy’s solution |
Enucleation & cryotherapy |
Marsupialization/ decompression alone |
Decompression & residual cystectomy |
Resection
|
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]
- Yearly follow-up for at least 5 years
- Orthopantogram every year, MRI every 2 years
References[edit]
- ↑ 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.