Odontogenic cysts Flashcards
What is a cyst?
- A pathological cavity containing fluid or gas.
- Not created by the accumulation of pus.
- Most are lined by epithelium (but not all)
- The site of origin is often obvious.
In the jaws all odontogenic cysts are ________, but a number of cystic lesions, which included in the differential diagnosis, are not. They are derived from epithelial residues of tooth forming organ.
epithelium lined
What problems do cysts cause?
- Increase in size
- Damage or displacement of teeth
- Vital structures damaged (e.g. IAN compression injury)
- Infection
- Pain
- Bone resorption – pathological fractures e.g. with chewing
Cysts are common, and there are several classifications used to describe them which overlap with each other. List the classification of odontogenic cysts.
Odontogenic cysts of inflammatory origin:
* Radicular cyst (70%)
* Residual cyst
Inflammatory collateral cysts
* Paradental cyst
* Mandibular buccal bifurcation cyst
Odontogenic & non- odontogenic developmental cysts: (non inflammatory)
* Dentigerous cyst (15%)
* Eruption cyst
* Odontogenic keratocyst (10%)
* Lateral periodontal cyst (5%)
* Botryoid odontogenic cyst
* Gingival cysts(5%)
* gingival cysts of adults
* gingival cysts of infants (alveolar cyst)
* Glandular odontogenic cyst (5%)
* Calcifying odontogenic cyst (5%)
* Orthokeratinised odontogenic cyst (5%)
Which cells do odontogenic cysts develop from?
o Epithelial rests of Serres
o Reduced enamel epithelium
o Rests of malassez
Give examples of cystic lesions that are not epithelium lined.
E.g., solitary bone cyst, aneurysmal bone cyst which may be included in a classification as ‘bone cysts’.
Generally, cysts whereby the epithelial lining is derived from remnants of the tooth forming tissue are formed odontogenic, and further subdivided into ____________ and _________ cysts.
Inflammatory and developmental
What are cysts whose epithelial lining is derived from sources other than tooth forming tissues classified as?
Non-odontogenic. (developmental)
What are the incidence of cysts?
90% odontogenic
10% non odontogenic
Describe the mechanism of Cystic growth.
Need source of epithelium, stimulus for epithelial proliferation and mechanism of growth & bone resorption:
- Inflammation causes epithelium proliferation and the cells in the cyst centrally breakdown. Increased osmotic pressure thereby draws the water inwards.
- Bone resorption occurs due to the release of collagenase and prostaglandins by fibroblasts, osteoclasts and stimulating factors.
- Initially bony hard swelling forms, which becomes thinner and you get egg shell like crackling, which can then become a fluctuant swelling.
What are the key features of a cyst?
- Form sharply defined radiolucency’s (>20mm more likely to be cyst) – round or ovoid shape, surrounded by a narrow, radiopaque or corticated margin and extends to lamina dura of involved tooth. (MUST consider keratocyst as differential diagnosis)
- Fluid may be aspirated, and some thin-walled cysts can be transilluminated (difficult intra-orally)
- Slow growing, displace rather than resorb teeth
- Symptomless unless infected and often incidental findings on radiographs – important not to leave as can lead to infection, displacement of local structures like teeth / neurological structures.
- If symptomatic: can cause movement of teeth, discreet swelling, infection, pain
- Rarely large enough to cause pathological fractures if bone resorption occurs.
- Form compressible and fluctuant swellings if extending into the soft tissues
- Appear bluish when close to the mucosal surface
What is a radicular cyst?
- Most common of all odontogenic cysts, account for over 50% of jaw cysts
- Usually found at apex of tooth – arise due to proliferation of epithelial remnants of PDL as a result of periapical periodontitis due to death of pulp.
- Usually asymptomatic – incidental finding on rads – well defined, corticated radiolucency. Usually unilocular but can be multilocular always associated with non-vital tooth
- Long term: can cause swelling, bony expansion.
- Rarely occur before 10 years of age usually 30-50 yrs of age. More common in males
How does a radicular cyst grow?
- Due to chronic inflammation in the peri-radicular tissues resulting in a periapical granuloma stimulating the epithelium rests of Malassez.
- Following this there is central degeneration and necrosis which causes the formation of a cavity (lined by epithelium).
- Cyst expansion occurs via hydrostatic pressure as debris accumulates centrally.
- Radicular cysts are always associated with a non-vital tooth, and this is important diagnostically. May get infection.
- More common in maxilla (highest in anterior region)
What is the treatment for radicular cyst?
Enucleation – soft tissue over the cyst is lifted, and cyst removed/nucleated – cystic capsule completely removed reducing possibility of recurrence. Remaining cavity thoroughly cleaned & tight closure completed.
What is a residual cyst?
- These are radicular cysts which remain in situ after the tooth/teeth have been removed.
- Although the histological features are very similar, the source of the inflammation has been removed therefore the wall of a residual cyst may mature and become relatively uninflamed with a thin and irregular lining.
What is the treatment for residual cyst?
Enucleation
- Consider vital structures e.g. on OPT consider mental nerve
What is a Lateral Periodontal Cyst?
- Cysts that arise on lateral surface of a tooth root. (between roots of erupted teeth- usually mid 1/3 of root on rads)
- Developmental odontogenic cyst
- They are rare and often asymptomatic, hence usually found as an incidental radiographic finding. Vital teeth.
- Premolar and canine regions most common.
- Histology shows a simple stratified squamous epithelium lining, sometimes with the addition of epithelial plaques or thickenings.
- Radiographically depicted by a unilocular radiolucency lateral to the tooth. Adjacent teeth are usually vital.
*Common in adults 50s, 60s. Mean 47 yrs of age. - Tx: enucleation
What are the radiological features of a lateral periodontal cyst?
- Round / ovoid.
- Well circumscribed radiolucent area.
- Corticated, sclerotic margin. PDL space expanded.
- May become tear / pear shaped if teeth are displaced
What is a botryoid odontogenic cyst?
- Multi-cystic variation of the lateral periodontal cyst. (bigger and often recur)
- Rare
- 75% mandibular. Common in canine / premolar area
- 50% presents with swelling of bony expansion
- Common ages 50-70
What is a Dentigerous Cyst?
- Odontogenic cyst that encloses the crown of an unerupted tooth
- Lined by epithelium which is derived from the reduced enamel epithelium.
- Usually attaches to the cervical aspect of cemento-enamel junction
- Develops from expansion of the follicle
- Commonly associated with mandibular third molars, premolars, canines and max canines, although their distribution is directly comparable to impacted teeth frequency.
- It may displace the impacted tooth and prevent its eruption.
- Often an incidental finding on a radiograph.
- Slowly enlarging swelling, can sometimes be painful, infected.
Describe the epidemiology of a Dentigerous Cyst?
o Most common developmental odontogenic cyst.
o Approximately 20% of all odontogenic cysts, and 60% of developmental cysts.
o More common in males.
o Rare in children
What is the tx of a Dentigerous Cyst?
- Marsupialization – conservative surgical intervention that decreases the size of cyst gradually.
- Enucleation
- Extraction of the tooth
What is an eruption cyst?
- Cysts that occur on the mucosa of a tooth prior to eruption. More common in children.
- Most frequently found overlying deciduous incisors or first permanent molars.
- In effect a ‘superficial dentigerous cyst’ - most ‘burst’ spontaneously, and rarely are painful or become infected. Soft, fluctuant.
What is the tx of an eruption cyst?
Marsupialization, and the underlying tooth will usually erupt spontaneously.
What is an Odontogenic Keratocyst (OKC)?
Previously been described as a keratocystic odontogenic tumour within the classification of odontogenic tumours.
- High recurrence rate (25-60%.)
- Permeative growth pattern. Often unilocular radiolucency but can be multilocular. Corticated margin.
- Presence of satellite cysts and budding.
- All of which indicate aggressive behaviour and consistent with a neoplasm.
- It is important to note that the OKC is associated with mutations in the PTCH tumour suppressor gene which is responsible for basal cell carcinomas.
- More common in the mandible, and often asymptomatic unless swelling.
- They extend through the path of least resistance and often through the ramus and body of the mandible prior to causing obvious bony expansion.
- Occur in patients over a wide age range
How does an odontogenic keratocyst arise?
The OKC arises from the remnants of the dental lamina and is very distinctive, therefore diagnosis is not usually a problem.
Describe the histopathology of an odontogenic keratocyst.
- Connective tissue wall is uninflamed, and lined by parakeratinsed stratified squamous epithelium, with a characteristic corrugated surface.
- Basal epithelial layer is well defined, with palisaded basal cells with reversal of nuclear polarity.
What are the Radiographic features of an odontogenic keratocyst?
o Well defined, often with a rounded or scalloped margin.
o Can be unilocular or multilocular
o May envelope a tooth and therefore be difficult to distinguish between a dentigerous cyst.
o May displace adjacent teeth and inferior alveolar nerve canal.
o Multiple OKC’s in the same patient are one of the consistent features of ‘Gorlin Goltz Syndrome or Basal Cell Naevus. This comprises of a triad of multiple basal cell naevi, odontogenic keratocysts of the jaws and skeletal anomalies.
What other features are OKC’s associated with?
Basal cell carcinomas, pitting of palms and soles of feet and calcification of Falx Cerebri.
What are the major and minor criteria of Gorlin Goltz Syndrome?
Major:
Multiple basal cell carcinomas or single BCC <20 years
Odontogenic keratocyst of the jaw
3 or more palmar or palmar pits
Falx cerebri calcification
Rib anomalies (bifid, fused or splayed)
First degree relative with basal cell nevus syndrome
Minor:
Rib anomalies (bifid, fused or splayed)
Other specific skeletal & radiological abnormalities
Macrocephaly
Cleft lip or palate
Ovarian or cardiac fibroma
Lymphmesenteric cysts
Ocular anomalies
What are the Characteristic Features of an odontogenic keratocyst?
- Frontal and parietal bossing & broad nasal root
- Multiple OKCs of the jaws
- Multiple naevoid BCCs of the skin
- Skeletal anomalies (bifid ribs and abnormalities of the vertebrae)
- Intra-cranial anomalies (e.g., calcification of falx cerebri and abnormally shaped sella turcica)
- CLP in ~5%
What is the tx for an odontogenic keratocyst?
Treatment: Enucleation +/- resection
Recurrence rates are high
Long term follow-up and regular imaging
What are Calcifying odontogenic cysts?
- Rare cysts
- Histology: odontogenic cysts lined by ameloblastoma like epithelium.
- Focal accumulations of ghost cells which may calcify
- Average age 30 yo
- Common in maxilla
- Radiological interpretation: well defined, corticated margins, usually unilocular. Can be associated with an odontoma.
What are Glandular odontogenic cyst?
- Rare cysts
- Histology: epithelium resembles salivary / glandular tissue.
- Present around 50 yrs of age
- In Mandible – often crosses midline & symmetrical
- Radiological interpretation: well defined, corticated, uni or multilocular. Sometimes dentigerous relationship.
- Recurrence rare.
