odontogenic tumours Flashcards
How are odontogenic tumours classified?
Based on tissue of origin:
- epithelial
- mesenchymal
- mixed (epithelial and mesenchymal)
What type of odontogenic tumours can have dentine/enamel formation and why is this?
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
What are the odontogenic sources of epithelium that form odontogenic tumours?
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
Give 3 examples of odontogenic tumours?
Ameloblastoma
Adenomatoid odontogenic tumour
Calcifying odontogenic tumour
Give an example of a mesenchymal odontogenic tumour
Odontogenic myxoma
Give an example of a mixed odontogenic tumour
Odontoma (odontomes)
How do odontogenic tumours appear radiographically?
Highly variable - can be entirely radiolucent, mixed or entirely radiopaque
May change as tumour progresses
50% of cases are either ameloblastoma or odontoma
Describe the presentation of an ameloblastoma
Benign epithelial tumour
Locally destructive but slow-growing
Typically painless
What is the incidence of ameloblastomas?
Makes up 1% of oral and maxillofacial tumours
Most common in 4th-6th decades
80% occur in posterior mandible
Affects males more than females
What are the radiological types of ameloblastoma?
Multicystic (85-90%)
Unicystic - affects younger patients and has a lower recurrence risk
What are the histological types of ameloblastoma?
Follicular
Plexiform
Desmoplastic
Several other less common types
Describe the margins of ameloblastomas
Usually well-defined and corticated
Potentially scalloped
If Multicystic have thick curved septa giving a soap-bubble appearance
How do ameloblastomas affect adjacent structures?
May cause displacement of structures, thinning of bony cortices and a knife edge external root resorption
Describe the histology of follicular ameloblastomas
Ameloblast-like cells
Stellate reticulum like tissue
Cystic changes and fibrous changes are seen
Describe the histology of Plexiform ameloblastomas
Ameloblast-like cells are seen in between stellate reticulum-like tissues
Fibrous tissue present
What are Adenomatoid odontogenic tumours (AOT) and how does it present?
A benign epithelial tumour
Classically presents as a unilocular radiolucency with internal calcifications around crown of unerupted maxillary canine
What is the incidence of AOTs?
Makes up 3% of odontogenic tumours
Most common in 2nd decades
Affects females more than males
Majority occur in anterior maxilla
How do AOTs present radiographically?
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
Describe the histology of AOTs
Duct like structure seen
Distinctive patchy calcification seen
Recurrence rate very low
What are calcifying epithelial odontogenic tumours (CEOT)?
A benign epithelial tumour
Aka - Pindborg tumour
What is the incidence of CEOTs?
Makes up 1% of odontogenic tumours
Most common in 5th decade
Affects males more than females
Posterior mandible is most common site
How do CEOT present?
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
What is an odontogenic myxoma?
A benign mesenchymal tumour
What is the incidence of odontogenic myxomas?
Makes up 3-6% of odontogenic tumours
Most common in 3rd decade
Equal male to female ratio
More common in the mandible
How do odontogenic myxomas present?
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
Describe the histology of odontogenic myxomas
Loose myxoid tissue with stellate cells
May contain islands of inactive odontogenic epithelium
No capsule so is locally invasive
How are odontogenic myxomas managed?
Curettage or resection depending on size
High recurrence rate - 25%
Follow up is important
Lower recurrence rate if unilocular
What is an odontoma?
A benign mixed tumour
Technically a hamartoma
Malformation of dental tissue - enamel, dentine, cementum and pulp
What similarities do odontomes have to teeth?
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
What is the incidence of odontomes?
1/5 to 2/3 of all odontogenic tumours
Most common in 2nd decade
Affects males and females equally
What are the types of odontomes?
Compound
Complex
Describe compound odontomes and where they are found
Ordered dental structures
May appear as multiple mini teeth ie - denticles
More common in the anterior maxilla
Describe complex odontomes and where they are found
Disorganised mass of dental tissues
More common in posterior body of mandible
What type of odontome is more common?
Compound more common than complex with 2:1 ratio
Describe the histology of odontomes
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
