OP17 non-odontogenic cysts

Question 1

What is a non-odontogenic cyst?

Answer 1

A cyst that is not related to epithelial residues of the tooth forming organ.

Question 2

What are the different epithelised and non-epithelised bone cysts?

Answer 2

Epithelised bone cysts - nasopalatine cyst, nasolabial cyst, median palatine/median alveolar/median mandibular, globulomaxillary cyst
Non-epithelised primary bone cysts - solitary bone cyst, aneurismal bone cyst, Stafne’s idiopathic bone cavity

Question 3

What are the different types of soft tissue cysts?

Answer 3

Salivary gland cysts - mucous retention, mucous extravasation, lymphoepithelial
Floor of mouth cysts - ranula, dermoid and epidermoid, lymphoepithelial
Antral cysts - pseudocyst of maxillary antrum, mucoceles, post-surgical maxillary cyst
Cysts of the neck - branchial cyst, thyroglossal cyst

Question 4

What is the most common non-odontogenic cyst of the jaw?

Answer 4

Nasopalatine cyst

Question 5

What is the origin of the nasopalatine cyst?

Answer 5

Nasopalatine duct epithelial embryonic residues.

Question 6

How do nasopalatine cysts present clinically?

Answer 6

Asymptomatic or pain on pressure, anterior swelling, discharge (salty taste: mucoid; foul taste: purulent)

Question 7

How to nasopalatine cysts present on x-rays?

Answer 7

USO x-ray
Round, ovoid, heart shaped, sclerotic rim, DD from normal incisive fossa (>6mm –> cyst)

Question 8

What is the histology of the lining and connective tissue of nasopalatine cysts?

Answer 8

Lining: stratfied squamous, pseudostratified ciliated columnar (respiratory), mucous cells, cuboidal epithelium, combinations
Connective tissue with neurovascular bundles, some mucous glands, chronic inflammatory cell infiltration

Question 9

What is the origin of the nasolabial cyst?

Answer 9

Nasolacrimal duct epithelial embryonic residues
(duct from angle of the eye for nasal caviuty under 3rd meatus)

Question 10

Where are nasolabial cysts most commonly found?

Answer 10

In soft tissue of upper lip, below alar of nose

Question 11

What symptoms do nasolabial cysts cause?

Answer 11

Swelling, sometimes painful or causing breathing difficulty

Question 12

How do nasolabial cysts present on radiograph?

Answer 12

Increased radiolucency at apex of incisor teeth

Question 13

What is the histology of the lining and cyst wall in a nasolabial cyst?

Answer 13

Lining: non/ciliated pseudostratified columnar epithelium + goblet cells, squamous metaplasia, cuboidal ep.
Cyst wall: relatively acellular connective tissue

Question 14

Describe median cysts and globulomaxillary cysts

Answer 14

Median palatine, median alveolar cysts - likely posterior extensions of palatine duct cysts
Median mandibular cyst
Globulomaxillary cyst between vital lateral incisor and canine.

Basso just variants of other cysts

Question 15

What is the origin of solitary bone cyst (traumatic/haemorrhagic/unicameral bone cyst)

Answer 15

Trauma with medullary haemorrhage? –> clot liquefaction. Heals following surgical exploration.

Question 16

Describe solitary bone cysts

Answer 16

Molar/premolar area in mandible
Asymptomatic
Bone expansion in 25%
Single lesions, non-epithelised, no acute or prolonged infection

Question 17

Are solitary bone cysts real cysts?

Answer 17

No because they dont have an epithelial lining

Question 18

How do solitary bone cysts present on x-ray?

Answer 18

Scalloping between teeth and remote areas too.

Question 19

What is the histology of bone cysts?

Answer 19

Contains air or some gas, blood, serous fluid
Bony walls covered by loose, vascular fibrous tissue, haemosiderin, multinucleated giant cells
No lining

Question 20

Where are aneurysmal bone cysts found and are they primary or secondary lesions?

Answer 20

Posterior mandible
Primary lesions, or secondary to fibroosseous lesions and giant cell granuloma

Question 21

What do aneurysmal bone cysts cause and why?

Answer 21

Firm expansive swelling, balloon cortex, can be painful
Perhaps associated to haemodynamic disturbance in the medullary bone

Question 22

How do aneurysmal bone cysts present on x-ray?

Answer 22

Uni or multilocular radiolucencies

Question 23

What is the histology of aneurysmal bone cysts?

Answer 23

Numerous no-endothelium lined blood filled spaces and cellular fibrous tissue, haemorrhage, haemosiderin, multinucleated giant cells
No lining

Question 24

What is Stafne’s idiopathic bone cavity?

Answer 24

Developmental anomaly of the mandible. Round or oval well demarcated defect. Usually between premolar region and angle of the mandible, below the alveolar nerve canal on the lingual side.

Question 25

What does a Stafne's bone cavity contain?

Answer 25

Ectopic submandibular salivary gland tissue

Question 26

How do you confirm a Stafne's bone cavity?

Answer 26

Confirm with a sialograph (usually chance finding on x-ray)

Question 27

What are mucous extravasation cysts?

Answer 27

Mucoceles mainly found on the lower lip. A bluish translucent submucosal swelling. They extravasate mucus from the ruptured duct.

Question 28

What is the histology of mucous extravasation cysts?

Answer 28

Mucin filled cavity, granulation tissue wall, no epithelial lining, chronic inflammation, 'foam cells', torn duct might be visible.

Question 29

What lines a mucous extravasation cyst if it is not epithelium?

Answer 29

Granulation tissue

Question 30

What causes a mucous retention cyst?

Answer 30

Partially obstructed duct eg by calculus, cells, mucous, to cause the accumulation of saliva

Question 31

What is the histology of a mucous retention cyst?

Answer 31

Dilation of duct, lined by ductal epithelium, no surrounding chronic inflammation/

Question 32

Why is there no inflammation in a mucous retention cyst?

Answer 32

Because mucous remains insulated from the connective tissue by the lining of the duct

Question 33

What can mucous retention cysts turn into and how?

Answer 33

If the cyst bursts and the epithelial lining breaks down, it can form a mucous extravasation cyst.

Question 34

What are mucous extravasation cysts called if they are found in the floor of the mouth?

Answer 34

Ranula (not common in lower lip)

Question 35

When do mucous retention cysts most likely get bigger?

Answer 35

Before a meal - higher secretions of saliva

Question 36

Where are lymphoepithelial cysts most likely found?

Answer 36

Rare but in FoM, lateral neck, parotid gland

Question 37

What is the histology of lymphoepithelial cysts?

Answer 37

Cyst lined by stratified squamous epithelium entrapped by lymphoid tissue Serous fluid with desquamated epithelium and lymphocytes

Question 38

How are ranulas treated?

Answer 38

Marsupialisation - cut open with a pouch in the lesion Resection Gland resection

Question 39

Where do rare dermoid and epidermoid cysts occur?

Answer 39

Many sites including FoM Intraoral or submental (midline)

Question 40

How do dermoid/epidermoid cysts occur?

Answer 40

Epithelium enclavement during fusion of mandibular and hyoid branchial arches

Question 41

What is the difference between dermoid and epidermoid cysts?

Answer 41

When the cyst wall has skin appendages (hair follicles, sebaceous gland, sweat glands or erector pili muscles), they are called dermoid cysts, otherwise epidermoid.

Question 42

What is the histology of dermoid/epidermoid cysts?

Answer 42

Lined by orthokeratinised stratified squamous epithelium, keratin debris in lumen

Question 43

What is a pseudocyst of the maxillary antrum?

Answer 43

Soft tissue elevation from the floor of the maxillary sinus, with an accumulation of inflammatory exudate, no mucine!

Question 44

How does a pseudocyst of maxillary antrum present on an x-ray?

Answer 44

Dome shaped radiopacity

Question 45

How do mucoceles of the antrum form?

Answer 45

Mucous retention cysts form as a consequence of rhinitis and sinusitis. The maxillary ostium is blocked from no drainage, forming mucoceles.

Question 46

What is histology of mucoceles of the antrum?

Answer 46

Same as those in salivary glands Epithelium is from antrum lining

Question 47

What happens if the mucoceles in the antrum rupture?

Answer 47

The mucus stimulates granulation tissue forming a mucous extravasation cyst

Question 48

Describe post surgical maxillary cyst of the antrum

Answer 48

Pain, swelling, pus discharge Post-surgery cyst Epithelial antral lining rests are left behind in surgery forming cysts Mostly located in the antero-lateral wall of sinus Histology: thin epithelium lining which may have inflammatory infiltration in the capsule

Question 49

What are branchial cysts?

Answer 49

Same as lymphoepithelial cysts Epithelium (salivary gland) entrapped in cervical lymph node

Question 50

Where are branchial cysts of the neck most commonly found?

Answer 50

Angle of the mandible, anterior sternomastoid muscle border

Question 51

What do branchial cysts look like and how do we confirm them?

Answer 51

Asymptomatic moveable masses Clear with transillumination

Question 52

What happens if a mass if opaque with transillumination?

Answer 52

Might be blood, lymph node, neoplasm

Question 53

Where does the thyroglossal duct cyst develop from?

Answer 53

Embryonic thyroglossal duct (duct from midline of tongue foramen caecum, to thyroid gland)

Question 54

Where are most thyroglossal duct cysts found?

Answer 54

Near the hyoid bone

Question 55

What is the lining and contents of the thyroglossal duct cyst?

Answer 55

Lining is stratified squamous ciliated columnar epithelium. Wall can contain thyroid, lymphoid tissue, mucous glands.

Question 56

What symptom can thyroglossal duct cysts cause?

Answer 56

Dysphagia