Cysts of the Jaw and Other Orofacial Tissues

Question 1

Define a cyst

Answer 1

A pathological epithelial lined cavity within tissue that can be filled with fluid or gas (not created by the formation of pus)

Question 2

How do we classify cysts?

Answer 2

Cysts are classified into:

Hard tissue cysts

Soft tissue cysts

Hard tissue cysts are further divided into:

Odontogenic cysts (arising from the tooth or tooth forming structures)

Non-odontogenic cysts (arising from the fusion of plates, processes or the premaxilla during embryological development of the face)

Non-epithelial lined cysts (present like cysts but are not truly cysts as they are not epithelial lined cavities)

Soft tissue cysts are further divided into:

Developmental cysts

Non-developmental cysts

Question 3

Briefly describe why cysts can form

Answer 3

Epithelium is a particular kind of tissue that is found on lining surfaces. Its nature means that it tends to try and cover things or exclude material from the body. This includes pathological cavities. When these pathological cavities become lined with epithelium, they become a cyst

Question 4

Why are some non-epithelialised cavities called cysts?

Answer 4

Although they are not true cysts, they present like cysts clinically and radiographically. We would not be able to determine that they are not cysts until we treat them and send them to histopathology

Question 5

Briefly describe the category of odontogenic cysts

Answer 5

A pathological epithelial lined cavity arising from the tooth forming tissues (epithelial cell rests, enamel follicle, enamel organ, dental lamina etc.)

There are many types, some of which are inflammatory (radicular cysts, residual cysts, paradental cysts) and some of which are non-inflammatory (dentigerous, keratocysts, lateral periodontal, calcifying odontogenic cyst, glandular odontogenic cyst)

Question 6

Odontogenic cysts can be classified into:

Answer 6

Inflammatory and non-inflammatory odontogenic cysts-

Inflammatory-
PA/radicular
Residual
Paradental

Non-inflammatory (developmental)-
Dentigerous
Keratocyst
Lateral periodontal
Calcifying odontogenic cyst
Glandular odontogenic cyst

Question 7

Describe the epidemiology of odontogenic cysts

Answer 7

Generally, very common.

70% of all odontogenic cysts will be radicular/PA cysts
15% of all odontogenic cysts will be dentigerous cysts
10% of all odontogenic cysts will be keratocysts
5% of all odontogenic cysts will encompass all other cyst forms

Question 8

Generally, how do cysts present?

Answer 8

Usually asymptomatic incidental findings on radiographs

Can be associated with movement or migration of teeth/other structures or failed eruption of teeth

May cause swellings that happen slowly over the course of months to years

Can become infected, in which case, they will cause pain and swelling (symptomatic).

If cysts in the lower jaw become large enough, they may be obstruct the function of the inferior alveolar nerve, leading to numbness in its distribution (lower lip, chin, teeth on affected side)

Typically well-defined, corticated radiolucencies

May be unilocular (single circular cyst) or multilocular (multiple locules within the cavity, with thin bony septa separating each of them from one another)

Question 9

Why are cysts a problem?

Answer 9

Although, they’re asymptomatic, cysts can grow, having the potential to move, loosen or damage teeth as well as other anatomical structures e.g., inferior alveolar nerve

If they get big enough, they may come close to the surface which can cause them to become infected and therefore symptomatic

If they get big enough, they can weaken the bone, leading to potential pathological fracture. This will occur at a very late stage of cyst development

As the cyst gets bigger, their treatment becomes much more complex and difficult to undertake. Therefore, they should be removed as soon as discovered, when they are much smaller

Question 10

Briefly describe the pathophysiology of a radicular cyst

Answer 10

Also known as a PA cyst

A carious tooth with a pulp that has died off due to caries progression will eventually result in chronic inflammation at the apex of the tooth

This inflammation causes proliferation of a number of cells around the apex of the tooth, including epithelial cells and cell rests of Malassez within the PDL. These expand to form a ball.

Initially, this radiolucency can represent a PA granuloma which is essentially a cavity containing epithelial cells, WBCs and debris.

If the granuloma persists because the tooth isn’t removed or doesn’t undergo RCT, we get central liquefaction and necrosis of the cells, leaving only epithelial cells around the outside of the cyst cavity. It is at this point the granuloma transforms into a PA cyst.

Question 11

How do radicular cysts present radiographically?

Answer 11

A well-defined, corticated, unilocular radiolucency almost always around the apex of a non-vital tooth.

May see evidence of non-vitality through deep caries (caries progression into the pulpal space), large restorations, RCT’d/crowned tooth, history of trauma to the tooth.

Question 12

What is a residual cyst?

Answer 12

If there was a tooth with an associated PA cyst that has now been removed without the removal of the cyst (has not been treated with enucleation etc.), the cyst may persist and as a result, we end up with a residual cyst.

Often seen underneath bridges

Question 13

Briefly describe the pathophysiology of a dentigerous cyst

Answer 13

Non-inflammatory, developmental cyst

As the crown of a tooth is completed and the enamel is laid down, the enamel follicle sits over it. This is the remnant of the enamel organ.

If the tooth doesn’t erupt, then some fluid can get caught between the enamel surface and the enamel follicle. This can start to expand and form a dentigerous cyst.

Question 14

List the features of a dentigerous cyst

Answer 14

Will be associated with the crown of an unerupted tooth. Will envelope the crown into the cavity.

The cyst will almost always end at the junction between the crown and the root (ACJ)

May displace/push the associated unerupted tooth

May cause resorption of other teeth/damage adjacent teeth

Question 15

What is the specific rationale to remove a dentigerous cyst with the associated unerupted tooth?

Answer 15

Want to eliminate the risk of displacing the unerupted tooth or damaging adjacent teeth (root resorption)

Question 16

Why do dentigerous cysts tend to almost always stop at the ACJ?

Answer 16

As this cyst type tends to be associated with the crown of an unerupted tooth, they tend to be limited by the ACJ (limit of the enamel at the neck of the tooth, just before it starts to form the root).

This is where the dental follicle is attached and so it makes sense that as the dental follicle expands, the edges of it will remain attached to the ACJ. As a result, a dentigerous cyst tends to almost always appear to stop at the ACJ.

But not always, can envelope the tooth much more extensively if the cyst is able to get big enough.

Question 17

What tooth forming structure does an odontogenic keratocyst arise from?

Answer 17

Dental lamina

Question 18

What tooth forming structure does a radicular cyst arise from?

Answer 18

Epithelial cell tests of Malassez within the PDL

Question 19

What tooth forming structure does a residual cyst arise from?

Answer 19

Epithelial cell rests of Malassez within the PDL

Question 20

What tooth forming structure does a dentigerous cyst arise from?

Answer 20

Enamel follicle

Question 21

What tooth forming structure does a lateral periodontal cyst arise from?

Answer 21

Unknown, could be the enamel follicle or dental lamina

Some even propose it is the epithelial cell rests of Malassez within the PDL

Question 22

Which cyst has the highest recurrence rate and is the most difficult to treat out of all odontogenic cysts?

Answer 22

Odontogenic keratocysts

Question 23

Why do odontogenic keratocysts have a high recurrence rate?

Answer 23

These cysts are very difficult to treat because they tend to have multiple locules and so it becomes easy to miss one locule during enucleation and not remove the entire cystic tissue.

To add, the cyst lining tends to be very delicate and friable, therefore it is very easy to leave some cystic tissue behind

The residual cystic tissue that is left behind, then has a chance to persist and continue to grow

Question 24

List the features of an odontogenic keratocyst

Answer 24

Likely a well defined, corticated multilocular (rather than unilocular) radiolucency

Affects the mandible more than the maxilla, but can be seen in both

Can present anywhere but most commonly seen in the angle of the mandible around where the wisdom tooth should be (50%)

May be associated with an unerupted tooth

Can be quite extensive but tend to cause minimal expansion and therefore we don’t tend to see a lot of swelling (will require the cyst to erode through the ramus and the body of the mandible before causing expansion/swelling)

Can damage adjacent teeth

Question 25

If a patient presents with multiple odontogenic keratocysts to your clinic, what should you suspect?

Answer 25

Consider the possibility the patient may have undiagnosed Gorlin Goltz syndrome

Assess patient for features of the syndrome such as facial bossing (prominent forehead), hypertelorism (wide inter-eye distance), multiple basal cell naevi on the skin, skeletal abnormalities

Refer patient to GP for definitive diagnosis, if suspected

Question 26

Gorlin Goltz syndrome is associated with which odontogenic cyst?

Answer 26

Odontogenic kerayocysts

Question 27

List the features of Gorlin Goltz syndrome

Answer 27

Multiple odontogenic keratocysts

Skeletal abnormalities

Facial bossing (prominent forehead)

Multiple basal cell naevi

Hypertelorism (wide inter-eye distance)

Question 28

Where are we most likely to find an odontogenic keratocyst?

Answer 28

Mandible>maxilla

Angle of the mandible

Question 29

Briefly describe the features of an eruption cyst

Answer 29

Associated with erupting teeth, often considered a superficial dentigerous cyst

Occurs in kids, just as a tooth is about to erupt

Swelling tends to take a bluish shade and appear round. Located where we expect a tooth to erupt

Most self-resolve, rupturing spontaneously as the tooth underlying them erupts and becomes exposed

Will not see a radiolucency outside the bone

Question 30

How is an eruption cyst treated?

Answer 30

Most self-resolve, rupturing spontaneously as the tooth underlying them erupts and becomes exposed.

Therefore tend to not need any active intervention unless the cyst is causing symptoms, in which case an incision may be made to de-roof the cyst

Question 31

Briefly describe the pathophysiology of an eruption cyst

Answer 31

The enamel follicle that has been assisting the tooth in its eruption process forms a cyst.

Essentially, a superficial dentigerous cyst

Question 32

List the features of a lateral periodontal cyst

Answer 32

Non-inflammatory, developmental cyst

Well-defined, corticated, unilocular radiolucency associated with a vital tooth

Located mesial or distal to the associated tooth (at the side), between the ACJ and the apex of the tooth

Tear-drop shaped. As there is more space between the apices of the teeth then there is at the crown margin, the cyst appears slightly wider in the direction of the apex, resulting in this shape

Question 33

What is the botryoid variant?

Answer 33

Multilocular variant of a lateral periodontal cyst

Well defined multilocular radiolucency located at the side of a tooth, between the ACJ and the apex

Has a tear drop shape

Question 34

List the features of a glandular odontogenic cyst

Answer 34

Rare non-inflammatory, developmental cyst. But display variable behaviour, so some argue they are not cysts but low grade tumours

May be found in association with odontogenic keratocysts, ameloblastomas or other pathology

Well-defined, corticated, unilocular radiolucency that presents like other cysts

May be associated with non-vital teeth or unerupted teeth and therefore mistaken for radicular or dentigerous cysts

Contain some cuboidal glandular cells. Only able to determine this through histopathology, otherwise present like other cysts and may be mistaken for them

Recurrence more likely

Question 35

List the features of a calcifying odontogenic cyst

Answer 35

Rare non-inflammatory, developmental cyst. But display variable behaviour, so some argue they are not cysts but low grade tumours

May be found in association with odontogenic keratocysts, ameloblastomas or other pathology

Well-defined, corticated, unilocular radiolucency that presents like other cysts

Contain areas of calcification or odontoma formation within them (radiopacities within the larger radiolicency)

Recurrence more likely

Question 36

A well-defined, corticated unilocular radiolucency that appears to be associated with the crown of an unerupted wisdom tooth is seen on an OPT. List the differential diagnoses for this presentation and how you would reach the definitive diagnosis in this scenario.

Answer 36

Dentigerous cyst

Glandular odontogenic cyst

Odontogenic keratocyst (although these tend to rarely present as unilocular radiolucencies)

Only way to determine which cyst type this is to remove the cyst and send it to histopathology.

A histopathologist will conduct a histological exam to determine the cells within the cyst. If glandular epithelium is observed, this would mean the cyst is a glandular odontogenic cyst as opposed to the other forms who will have their own histological markers of differentiation

Question 37

List some non-odontogenic hard tissue cysts

Answer 37

Nasopalatine duct cyst

Globulomaxillary cyst

Median palatal cyst

Question 38

How do non-odontogenic hard tissue cysts form?

Answer 38

These cysts are developmental cysts but do not arise from tooth forming tissues.

Instead, they arise during the embryological development of the face due to the fusion of different hard tissue structures such as the palatal plates, processes and premaxilla.

As these structures fuse, we get lines of fusion. Where these lines of fusions form, we can get inclusion of the epithelium which can go on to form a cyst in the future

Question 39

How does a naso-palatine duct cyst arise?

Answer 39

Developmental, non-odontogenic cyst that arises from the fusion of hard tissue structures (fusion of 2 lateral palatal structures and the premaxilla at the front).

As these structures fuse, a line of fusion forms. Where this line of fusion forms, we can get an inclusion of the epithelium which can go on to form a cyst in the future

Question 40

How does a globulomaxillary cyst arise?

Answer 40

Developmental, non-odontogenic cyst that arises from the fusion of hard tissue structures (fusion of the premaxilla and the maxillary plates)

As these structures fuse, a line of fusion forms. Where this line of fusion forms, we can get an inclusion of the epithelium which can go on to form a cyst in the future

These cysts tend to be between the upper 2 and 3

Question 41

How does a median palatal cyst arise?

Answer 41

Developmental, non-odontogenic cyst that arises from the fusion of hard tissue structures (fusion of the palatal shelves)

As these structures fuse, a line of fusion forms. Where this line of fusion forms, we can get an inclusion of the epithelium which can go on to form a cyst in the future

Question 42

Describe the features of a nasopalatine duct cyst

Answer 42

Painless swelling on the hard palate, located behind the central incisors

On a radiograph, will present as a well defined, corticated, unilocular radiolucency between and slightly beyond the upper incisors

May cause displacement of the upper incisors

Question 43

Describe the features of a globulomaxillary cyst

Answer 43

Painless swelling on the buccal surfaces, often between the upper 2 and 3

On a radiograph, will present as a well defined, corticated, unilocular radiolucency

May cause displacement of the associated teeth

Question 44

Describe the features of a median palatal cyst

Answer 44

Painless swelling located on the hard palate

On a radiograph (upper occlusal), will present as a well defined, corticated, unilocular radiolucency located on the hard palate behind the central incisors (at a distance from them)

Question 45

What are non-epithelialised cysts? List some examples

Answer 45

Called cysts but are not actually cysts as they are not epithelial lined (but are cavities). Just present like cysts clinically and radiographically.

Staphne’s idiopathic bone cavity
Solitary bone cyst (also known as a traumatic bone cyst or a unicameral cyst)
Aneurysmal bone cyst

Question 46

How does a Staphne’s idiopathic bone cavity arise?

Answer 46

Essentially, an inclusion of normal submandibular gland tissue in the lingual aspect of the mandible

Requires no treatment

Question 47

How does a Staphne’s idiopathic bone cavity present on a radiograph?

Answer 47

Well defined, corticated, unilocular radiolucency

Located underneath the ID canal, not associated with the apex of a tooth or the crown of an unerupted tooth

Question 48

How does a Staphne’s idiopathic bone cavity present on a CT scan?

Answer 48

Indentation of the lingual aspect of the mandible

Question 49

Describe the features of a solitary bone cyst

Answer 49

Non-odontogenic, non-epithelial lined cavity

Patient may report a history of trauma in the area during childhood

On a radiograph, we will see a well defined unilocular radiolucency with no expansion or movement of associated teeth/adjacent structures

If they are opened, we will often see a fibrous tissue or endothelial lining. Won’t see much in the tissue, just some blood and a very thin lining which comes away quite easily.

Question 50

How are solitary bone cysts treated?

Answer 50

Cyst is opened up and a biopsy is taken from the cyst and sent to histopathology

Undergoes curettage and is then enucleated which tends to resolve it

Question 51

Describe the features of an aneurysmal bone cyst

Answer 51

Very rare, non-odontogenic, non-epithelial lined cavity, filled with blood

On a radiograph, will present as a moderately defined, corticated radiolucency with a soap bubble appearance and faint trabeculation within it (pseudolocular appearance)

Expansile lesion (balloon like)

On histological examination, we will see a cavity with a fibrous lining which is filled with blood

Question 52

Soft tissue cysts can be divided into:

Answer 52

Developmental

Non-developmental

Question 53

How do developmental soft tissue cysts arise? List some examples

Answer 53

As the fusion of the branchial arches and closure of the branchial cleft occur, we can get the inclusion of epithelium and epithelial structures (essentially get caught up in the process). This leads to the formation of developmental soft tissue cysts.

Dermoid cysts
Branchial cleft cysts
Thyroglossal duct cysts

Question 54

Describe the features of a dermoid cyst

Answer 54

Most common, developmental, soft tissue cyst in the head and neck. Caused by the inclusion of epithelium and epithelial structures as the midline and the soft tissue overlying it fuses (formed due to the fusion of branchial arches)

Tend to present as a sublingual swelling

Tend to be round, located in the lower midline behind the teeth in the FoM

Presents as a fairly robust bag of keratinised epithelium which very often contain hair and sweat glands (because of the nature of the tissue that forms them)

Question 55

Describe the features of a branchial cleft cyst

Answer 55

Can present as little round swellings around the neck region

In adults, they can present as fairly large neck swellings

Question 56

How do brancial cleft sinuses arise?

Answer 56

Sinuses are one ended openings which are epithelial lined. Formed from the closure of branchial clefts.

Very common in the structures that are formed by the 1/2/3rd branchial arches (mandible, part of the ear and the hyoid bone).

Question 57

Describe the features of a branchial cleft sinus

Answer 57

A swelling/lump with a central opening on the skin of the face/neck. Tend to develop below the chin/collarbone/neck.

Can fill up with fluid, tissue or discharge

Quite common in children

Don’t usually cause problems, just cosmetically problematic.

Question 58

How are branchial cleft sinuses different from branchial cleft cysts?

Answer 58

Although both are formed from the closure of branchial clefts, sinuses are one ended openings which are epithelial lined. A cyst is completely enclosed within the tissues, a sinus will have an opening that goes on to the surface.

Question 59

How do thryoglossal duct cysts arise?

Answer 59

The thyroid actually develops from tissues that originate in the foramen cecum (which is part of the posterior tongue, where the back of the anterior 2/3rds of the tongue and the junction with the posterior 1/3rd of the tongue are). This migrates down into the neck to form the thyroid tissues.

During this process, we can get a little bit of epithelial tissue caught along the way, which fails to move and can later on in life, form a midline thyroglossal duct cyst.

Question 60

Describe the features of a thryoglossal duct cyst

Answer 60

A swelling/lump in the midline of the neck, just below the chin

Question 61

List some non-developmental soft tissue cysts

Answer 61

Non-developmental soft tissue cysts tend to be associated with salivary gland tissue. Examples include-

Ranulas

Mucoceles

Question 62

Non-developmental soft tissue cysts tend to be associated with salivary gland tissues and can be divided into 2 sub-types. What are these sub-types?

Answer 62

Mucous retention cysts-
Blockage of saliva/mucous within the salivary gland or duct
Involves minor salivary glands

Mucous extravasation cysts-
Escape of saliva from traumatised salivary gland or duct
Involves minor salivary glands or sublingual salivary gland

Question 63

How does a mucous retention cyst arise?

Answer 63

Saliva and mucous get caught up within the salivary gland/duct causing an obstruction or blockage within it which causes the salivary gland/duct to swell up

Tend to form in minor salivary glands

Question 64

How does a mucous extravasation cyst arise?

Answer 64

Saliva escapes from a traumatised salivary gland/duct. Once the saliva gets out of the gland/duct that they are supposed to be contained by, the nature of epithelium allows the epithelium to migrate around the bag of escaped saliva to form an epithelial cyst lining.

Tends to involve minor salivary glands or the sublingual gland.

Question 65

Describe the features of a ranula

Answer 65

Non-developmental soft tissue cyst

Mucous extravasation cyst that forms on the floor of the mouth and involves either the minor salivary glands or sublingual gland.

Will present as a swelling in the FoM

Question 66

How does a ranula arise?

Answer 66

Essentially, a mucous extravasation cyst, so saliva escapes from the minor salivary glands or the sublingual salivary glands into the tissues (often following trauma to these areas).

Here, the epithelium will migrate around the escaped saliva, forming an epithelial lining

Question 67

Describe the features of a plunging ranula

Answer 67

Non-developmental soft tissue cyst

Mucous extravasation cyst that forms on the floor of the mouth and involves either the minor salivary glands or sublingual gland

Extends through the mylohyoid muscle to cause a neck swelling as well as a swelling in the FoM. This is because of a developmental defect in the mylohyoid muscle (hole in the muscle) which the ranula can squeeze through, giving a swelling that is partly in the mouth and partly in the neck

Question 68

A ranula is normally treated using IO excision. How does the treatment for a plunging ranula differ and why?

Answer 68

A plunging ranula presents as a swelling in the floor of the mouth but also in the neck.

This is because of a developmental defect in the mylohyoid muscle (hole in the muscle) which the ranula can squeeze through, to give a cystic swelling that is partly in the mouth and partly in the neck

If we only address the intra-oral component of a plunging ranula through excision, it would just come back because the entire cyst has not been removed. Need to take a combined I/O and E/O approach to treatment therefore.

Question 69

Describe the features of a lip mucocele

Answer 69

Mucous retention or mucous extravasation cyst (cannot tell until the cyst is removed)

Painless, soft fluid filled swelling on the lower lip

May appear bluish

More common in children

Often, patient will report a history of trauma

Question 70

How do lip mucoceles arise?

Answer 70

Can be mucous retention cysts or mucous extravasation cysts

Can be caused by retention of mucous and saliva within the minor salivary glands or the escape of saliva from traumatised minor salivary glands in the FoM or the sublingual gland

Cannot tell what the pathophysiology of the cyst is until it is removed

Question 71

List the methods that we can use to treat a lip mucocele

Answer 71

Excision (a cut made on top of the mucocele, removed using careful dissection). GOLD STANDARD approach, however comes with the risk of scarring, swelling, bleeding and bruising

Cryotherapy (involves liquid nitrogen or accelerated carbon dioxide to produce a very cold area on a probe. If we anaesthetise the area and place this cold probe on the tissues, we can freeze the tissues resulting in an ice ball. The ice ball expands and the ice crystals damage the cells and break down the cyst lining. And then the cyst resolves)

Question 72

Why is there is a high risk of recurrence of lip mucoceles following removal?

Answer 72

Possible that the entire cyst lining has not been removed.

Or they may reoccur because the lower lip has 100s of minor salivary glands and as we’re working on removing one mucocele, the minor salivary gland next to it can become traumatised/obstructed leading to the formation of another cyst

Question 73

A 12 year old patient presents with a soft fluid filled swelling on the lower lip. The swelling has a bluish tinge to it and the patient reports no pain. On inquiry, the patient states they dropped their phone on their lip not too long ago. What is the likely diagnosis and management for this patient?

Answer 73

Lower lip mucocele (mucous extravasation cyst as the patient reports a history of trauma to the associated region)

Excision (will require referral)

Question 74

A patient presents with a slow growing, painless swelling on their upper lip. The patient reports no history of trauma in the region. What is the likely diagnosis and management protocol for this patient?

Answer 74

A salivary gland tumour

Referral via the 2 week wait referral pathway to rule out malignancy

Question 75

A lower lip swelling is likely to be a ___________________ whereas an upper lip swelling is more likely to be a ___________________

Answer 75

Lip mucocele

Salivary gland tumour

Question 76

Name 2 cysts that have a fibrous tissue lining instead of an epithelium lining

Answer 76

Solitary bone cysts

Aneurysmal bone cysts