odontogenic tumours

Question 1

How are odontogenic tumours classified?

Answer 1

Based on tissue of origin:
- epithelial
- mesenchymal
- mixed (epithelial and mesenchymal)

Question 2

What type of odontogenic tumours can have dentine/enamel formation and why is this?

Answer 2

Only mixed tumours due to the concept of induction:
Dentine forms first from odontoblasts which are mesenchymal in origin
Ameloblasts don’t start forming enamel until dentine starts getting laid down
So the presence of dentine is needed for induction and maturation of ameloblasts for enamel formation

Question 3

What are the odontogenic sources of epithelium that form odontogenic tumours?

Answer 3

Rests of Malassez - remnants of Hertwig’s epithelial root sheath
Rests of Serres - remnants of the dental lamina
Reduced enamel epithelium - remnants of the enamel organ

Question 4

Give 3 examples of odontogenic tumours?

Answer 4

Ameloblastoma
Adenomatoid odontogenic tumour
Calcifying odontogenic tumour

Question 5

Give an example of a mesenchymal odontogenic tumour

Answer 5

Odontogenic myxoma

Question 6

Give an example of a mixed odontogenic tumour

Answer 6

Odontoma (odontomes)

Question 7

How do odontogenic tumours appear radiographically?

Answer 7

Highly variable - can be entirely radiolucent, mixed or entirely radiopaque
May change as tumour progresses
50% of cases are either ameloblastoma or odontoma

Question 8

Describe the presentation of an ameloblastoma

Answer 8

Benign epithelial tumour
Locally destructive but slow-growing
Typically painless

Question 9

What is the incidence of ameloblastomas?

Answer 9

Makes up 1% of oral and maxillofacial tumours
Most common in 4th-6th decades
80% occur in posterior mandible
Affects males more than females

Question 10

What are the radiological types of ameloblastoma?

Answer 10

Multicystic (85-90%)
Unicystic - affects younger patients and has a lower recurrence risk

Question 11

What are the histological types of ameloblastoma?

Answer 11

Follicular
Plexiform
Desmoplastic
Several other less common types

Question 12

Describe the margins of ameloblastomas

Answer 12

Usually well-defined and corticated
Potentially scalloped
If Multicystic have thick curved septa giving a soap-bubble appearance

Question 13

How do ameloblastomas affect adjacent structures?

Answer 13

May cause displacement of structures, thinning of bony cortices and a knife edge external root resorption

Question 14

Describe the histology of follicular ameloblastomas

Answer 14

Ameloblast-like cells
Stellate reticulum like tissue
Cystic changes and fibrous changes are seen

Question 15

Describe the histology of Plexiform ameloblastomas

Answer 15

Ameloblast-like cells are seen in between stellate reticulum-like tissues
Fibrous tissue present

Question 16

What are Adenomatoid odontogenic tumours (AOT) and how does it present?

Answer 16

A benign epithelial tumour
Classically presents as a unilocular radiolucency with internal calcifications around crown of unerupted maxillary canine

Question 17

What is the incidence of AOTs?

Answer 17

Makes up 3% of odontogenic tumours
Most common in 2nd decades
Affects females more than males
Majority occur in anterior maxilla

Question 18

How do AOTs present radiographically?

Answer 18

75% associated with an unerupted tooth - commonly a maxillary canine, similar to a dentigerous cysts but typically attached apical to the CEJ
Unilocular radiolucency
Majority have internal calcifications/radiopacities which increase as the tumour matures
Margins well-defined and corticated/sclerotic
May displace adjacent structures but ERR is rare

Question 19

Describe the histology of AOTs

Answer 19

Duct like structure seen
Distinctive patchy calcification seen
Recurrence rate very low

Question 20

What are calcifying epithelial odontogenic tumours (CEOT)?

Answer 20

A benign epithelial tumour
Aka - Pindborg tumour

Question 21

What is the incidence of CEOTs?

Answer 21

Makes up 1% of odontogenic tumours
Most common in 5th decade
Affects males more than females
Posterior mandible is most common site

Question 22

How do CEOT present?

Answer 22

Slow growing but can become large
Half are associated with an unerupted tooth
Radiolucency often with internal radiopacities - calcifications
Variable radiographic presentation otherwise - unilocular/multilocular, margins well/poor defined, internal septa can be fine/coarse/none at all

Question 23

What is an odontogenic myxoma?

Answer 23

A benign mesenchymal tumour

Question 24

What is the incidence of odontogenic myxomas?

Answer 24

Makes up 3-6% of odontogenic tumours
Most common in 3rd decade
Equal male to female ratio
More common in the mandible

Question 25

How do odontogenic myxomas present?

Answer 25

Well-defined radiolucency +/- thin corticated maergins Larger lesions tend to be multilocular with scalloped margins - soap bubble appearance Slow growth along bone before causing buccal-lingual expansion Scallops between teeth but larger lesions may cause displacement - ERR is rare

Question 26

Describe the histology of odontogenic myxomas

Answer 26

Loose myxoid tissue with stellate cells May contain islands of inactive odontogenic epithelium No capsule so is locally invasive

Question 27

How are odontogenic myxomas managed?

Answer 27

Curettage or resection depending on size High recurrence rate - 25% Follow up is important Lower recurrence rate if unilocular

Question 28

What is an odontoma?

Answer 28

A benign mixed tumour Technically a hamartoma Malformation of dental tissue - enamel, dentine, cementum and pulp

Question 29

What similarities do odontomes have to teeth?

Answer 29

Mature to a certain stage ie - do not grow indefinitely Can be associated with other odontogenic lesions eg - dentigerous cysts Surrounded by dental follicle Lie above the inferior alveolar canal

Question 30

What is the incidence of odontomes?

Answer 30

1/5 to 2/3 of all odontogenic tumours Most common in 2nd decade Affects males and females equally

Question 31

What are the types of odontomes?

Answer 31

Compound Complex

Question 32

Describe compound odontomes and where they are found

Answer 32

Ordered dental structures May appear as multiple mini teeth ie - denticles More common in the anterior maxilla

Question 33

Describe complex odontomes and where they are found

Answer 33

Disorganised mass of dental tissues More common in posterior body of mandible

Question 34

What type of odontome is more common?

Answer 34

Compound more common than complex with 2:1 ratio

Question 35

Describe the histology of odontomes

Answer 35

Will have dental hard tissue as it is a mixed odontogenic tumour Will see areas of enamel, dentine, cementum and pulp If enamel isn’t fully calcified it is more organic and may be present Acid during slide prep will dissolve the calcified enamel