8 - Odontogenic tumours

Question 1

What is the split of benign vs malignant odontogenic tumours?

Answer 1

100:1 benign:malignant

Question 2

How are odontogenic tumours classified?

Answer 2

• based on origin of tissue
• epithelial
• mesenchymal
• mixed

Question 3

What type of tumour can have enamel and dentine formation?

Answer 3

• mixed
• due concept of induction
• dentine is mesenchymal and enamel is epithelial, but dentine induces enamel production

Question 4

Give examples of epithelial odontogenic tumours.

Answer 4

• ameloblastoma
• adenomatoid odontogenic tumour
• calcifying epithelial odontogenic tumour

Question 5

Give examples of mesenchymal odontogenic tumours.

Answer 5

Odontogenic myxoma

Question 6

Give examples of mixed odontogenic tumours.

Answer 6

Odontoma

Question 7

What is an ameloblastoma?

Answer 7

• benign epithelial tumour
• locally destructive but slow growing
• painless
• high recurrence

Question 8

What is the incidence of ameloblastoma?

Answer 8

• 30-50 years
• 80% in posterior mandible
• M>F

Question 9

What are the radiological types of ameloblastoma?

Answer 9

• multicystic
• unicystic (younger patients, less recurrence)

Question 10

What are the histological types of ameloblastoma?

Answer 10

• follicular (most common)
• plexiform
• desmoplastic

Question 11

Describe the radiographic appearance of ameloblastoma.

Answer 11

• well defined, corticated margins
• multicystic are scalloped
• multicystic can have thick septae, giving “soap bubble” appearance
• primarily radiolucent
• can cause displacement of adjacent structures, thinning of bony cortices and knife edge root resorption

Question 12

What is the management of ameloblastoma?

Answer 12

Surgical resection with margin

Question 13

What is the risk of malignant transformation of ameloblastoma?

Answer 13

<1%

Question 14

What is the risk of recurrence of ameloblastoma?

Answer 14

15%

Question 15

What is adenomatoid odontogenic tumour (AOT)?

Answer 15

• benign epithelial tumour
• 75% associated with unerupted tooth
• impedes eruption of associated tooth

Question 16

What is the incidence of AOT?

Answer 16

• teenagers
• F>M
• majority in anterior maxilla

Question 17

Describe the radiographic appearance of AOT.

Answer 17

• unilocular radiolucency with internal calcifications/radiopacities
• well defined, corticated/sclerotic margins that attach apical to CEJ (join PDL)
• may displace adjacent structures but root resorption rare

Question 18

Describe the histology of AOT.

Answer 18

• distinctive with patchy calcification
• fibrous tissue capsule
• duct like structures

Question 19

Describe the histology of follicular ameloblastoma.

Answer 19

• islands in fibrous tissue
• cystic changes
• ameloblast like cells
• stellate reticulum like tissue

Question 20

Describe the histology of plexiform ameloblastoma.

Answer 20

• ameloblast like cells back to back
• stellate reticulum like tissue
• fibrous tissue

Question 21

What is CEOT?

Answer 21

• calcifying epithelial odontogenic tumour
• benign epithelial tumour
• aka Pindborg tumour
• slow growing but can become large
• 50% associated with unerupted tooth

Question 22

What is the incidence of CEOT?

Answer 22

• 40s
• M>F
• posterior mandible is most common site

Question 23

Describe the radiographic appearance of CEOT.

Answer 23

• radiolucency with internal radiopacities
• calcifications of varying sizes
• variable radiographic appearance otherwise

Question 24

What is an odontogenic myxoma?

Answer 24

• benign mesenchymal tumour
• slow growth along bone before causing notable bucco-lingual expansion
• locally invasive, high recurrence and difficult to remove

Question 25

Describe the radiographic appearance of odontogenic myxoma.

Answer 25

• well defined radiolucency ± thin corticated margin
• small lesions are unilocular
• large lesions are multilocular with scalloped margins
• “soap bubble” appearance common
• “tennis racket” appearance rare but indicative of odontogenic myxoma
• scallops between teeth in larger lesions can cause displacement of teeth but resorption rare

Question 26

Describe the histology of odontogenic myxoma.

Answer 26

• loose myxoid tissue with stellate cells
• may contain islands of inactive odontogenic epithelium
• no capsule and is locally invasive

Question 27

What is the management of odontogenic myxoma?

Answer 27

• curettage
• resection
• follow up important

Question 28

What is the risk of recurrence of odontogenic myxoma?

Answer 28

25%

Question 29

What is an odontoma?

Answer 29

• benign mixed tumour (technically hamartoma)
• malformation of dental tissue
• has similarities to teeth (does not grow indefinitely, associated with other odontogenic lesions, surrouned by follicle)
• always above IAN

Question 30

What is the incidence of odontomas?

Answer 30

• 2/3 of all odontogenic tumours
• teenagers
• F=M

Question 31

What are the different types of odontoma?

Answer 31

• compound
• complex

Question 32

What is a compound odontoma?

Answer 32

• ordered dental structures
• appear like mini teeth
• common in anterior maxilla

Question 33

What is a complex odontoma?

Answer 33

• disorganised mass of dental tissue
• common in posterior body of mandible