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My BDS4 > Odontogenic Tumours > Flashcards

Odontogenic Tumours Flashcards

1
Q

How are odontogenic tumours commonly diagnosed if they are asymptomatic? (3)

A

Often discovered due to non-eruption of teeth, late-stage bony expansion of the jaws (tumour present for a long time) or imaging for other reasons (i.e. incidental)

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2
Q

What are the 3 classifications of odontogenic tumours?

provide examples of each.

A

Epithelial
ameloblastoma, adenomatoid odontogenic tumour
calcifying epithelial odontogenic tumour

mesenchymal
odontogenic myxoma

mixed
odontome/odontome

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3
Q

What is unique about mixed odontogenic tumours?

Describe briefly how this occurs?

A
  • Only mixed tumours can have dental hard tissues within the tissues e.g. dentine/enamel (due to concept of induction)

Concept of induction:
- Cant have enamel without dentine first
- First dental hard tissue formed is dentine = formed from odontoblasts which are mesenchymal in origin
- Ameloblasts are mature and only form enamel when dentine has started to be laid down (presence of dentine is important for induction of maturation of ameloblasts and formation of enamel)

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4
Q

List and describe briefly the 3 odontogenic sources of epithelium.

A
  • Rests of Malassez
  • Remnants of Hertwig’s epithelial root sheath
  • Formed from inner and outer odontogenic epithelium
  • The HERS breaks down once the tissues are formed, however some clumps of cells can persist and remain within the PDL
  • These usually remain inactive (vital but don’t divide)
  • Something switches these on/stimulates them and they start to divide to from odontogenic cysts/tumours
  • Rests of Serres
  • Remnants of the dental lamina (responsible for formation of the tooth germs)
  • Same process occur with the lamina after the development of all the teeth however some clumps of cells remain = Rests of Serres
  • Reduced enamel epithelium
  • Remnants of the enamel organ
  • Enamel organ reduces after the crown is formed
  • The outer and inner EE become close and stellate reticulum is present between them
  • The REE covers the formed tooth crown
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5
Q

What is the most common odontogenic tumour - why is it difficult to say for definite?

A

> 50% of cases are either ameloblastoma or odontoma

  • Debate over which is most common (due to issues with data collection & overall scarcity) Ameloblastoma often stated as more common but studies are based on histopathology results – odontomas arguably not often sent for histopathological assessment as they have a characteristic appearance and benign = no indication for histopathological assessment and they are just removed
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6
Q

What is an ameloblastoma?

A

A Benign epithelial tumour which is locally destructive but slow-growing

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7
Q

Why is an amelobastoma concerning?

A

Locally destructive to surrounding tissues

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8
Q

In what age and in what sex are ameloblastomas most common?

A
  • Most common in 30-60 years old
  • M > F
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9
Q

Where in the mouth are ameloblastomas most commonly found?

A

80% occur in posterior mandible

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10
Q

How can we classify ameloblastomas? (5)

A

Radiological:
* Multicystic (85-90%)
* Unicystic
- Younger patients
- Lower recurrence risk

Histological:
* Follicular
* Plexiform
* Desmoplastic – has a characteristic appearance (much more radiopaque)

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11
Q

Describe the radiographic features of an ameloblastoma. (8)

A

Margins
- Well-defined and corticated
- Potentially scalloped (not seen in unicystic)

  • Multicystic type
  • May have thick, curved septa within the lesion = “soap bubble” appearance
  • Primarily radiolucent (but rare variants can be mostly radiopaque e.g. desmoplastic)
  • Adjacent structures
  • Displacement of structures
  • Thinning of bony cortices
  • “Knife edge” external root resorption of adjacent teeth (clean cut)

Also has a characteristic expansion of growth – expands in all directions equally.

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12
Q

Describe the histology of a follicular ameloblastoma. (6)

A
  • Islands present within a fibrous tissue background
  • Islands Bordered by cells that resemble the ameloblast e.g. columnar cells with a dark staining nucleus
  • Tissues in the middle of the follicle are loose (resemble stellate reticulum of tooth germ)
  • Can be cystic changes within the follicle
  • Other changes within the stellate reticulum like tissue involve squamous metaplasia or cells become granular etc
  • No connective tissue capsule (in any of the types) = cells can grow and infiltrate into the jaw bone = reason for high recurrence rate
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13
Q

why have follicular amelobastomas got such a high recurrence rate?

A
  • No connective tissue capsule (in any of the types) = cells can grow and infiltrate inot the jaw bone = reason for high recurrence rate
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14
Q

Describe the histology of a plexiform ameloblastoma. (4)

A
  • Amelobastoma cells arranged in strands
  • Between the strands there is stellate reticulum like tissue
  • Some Cells can form back to back with hardly any SR like tissue between
  • No connective tissue capsule (in any of the types) = cells can grow and infiltrate inot the jaw bone = reason for high recurrence rate
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15
Q

why have plexiform amelobastomas got such a high recurrence rate?

A
  • No connective tissue capsule (in any of the types) = cells can grow and infiltrate inot the jaw bone = reason for high recurrence rate
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16
Q

What is the tx option of choice for ameloblastomas and why? (2)

A
  • Surgical resection with a 1cm margin of healthy bone removed (since they are aggressive and recurrence is common - Up to 15% of cases)
  • Risk of malignant transformation (<1% of cases) = Ameloblastic carcinoma
17
Q

What is an Adenomatoid Odontogenic Tumour (AOT)?

A

A benign epithelial tumour

18
Q

How does an an Adenomatoid Odontogenic Tumour (AOT) present?

A

Unilocular radiolucency with internal calcifications around crown of unerupted maxillary canine (not always the case but this Is the most common presentation)

19
Q

List the radiographic features of an AOT. (7)

A
  • 75% associated with an unerupted tooth (Commonly a maxillary canine)
  • Similar to dentigerous cyst but typically attached apical to cemento-enamel junction
  • Impedes eruption
  • Unilocular radiolucency
  • Majority have internal calcifications/radiopacities which Increase as tumour matures
  • Margins well-defined & corticated/sclerotic
  • May displace adjacent structures but external root resorption is rare
20
Q

In what age and in what sex are AOT’s most common?

A
  • Most common in 10-20 years old
  • F > M
21
Q

In what are of the mouth is an AOT most commonly found?

A

Majority occur in anterior maxilla

22
Q

Describe the histology of an AOT. (3)

A
  • Epithelial cells arrange in duct like structures, sheets or rosette appearance
  • There is a degree of calcification which are reflected in the radiological appearance
  • Has a well developed fibrous tissue capsule surrounding therefore removal is easier and has a lower recurrence rate
23
Q

Why have AOTs got a lower recurrence rate than an ameloblastoma?

A

Has a well developed fibrous tissue capsule surrounding therefore removal is easier and has a lower recurrence rate

= ameloblastoma doesnt have a fibrous tissue capsule

24
Q

What is a Calcifying Epithelial Odontogenic Tumour (CEOT)?

What is it also known as?

A

Benign epithelial tumour a.k.a. Pindborg tumour

25
Q

In what age and in what sex are CEOT’s most common?

A
  • Most common in 5th decade
  • M > F
26
Q

In what are of the mouth is an CEOT most commonly found?

A
  • Posterior mandible
27
Q

How do Calcifying Epithelial Odontogenic Tumour (CEOT) present? (8)

A
  • Slow-growing but can become large
  • Half are associated with an unerupted tooth
  • Radiolucency often with internal radiopacities
  • Calcifications of varying sizes
  • Variable radiographic presentation otherwise
  • Unilocular / multilocular
  • Margins: well-defined / poorly-defined
  • Internal septa: none / fine / coarse
28
Q

What is an odontogenic myxoma?

A

A benign mesenchymal tumour

29
Q

In what age and in what sex are odontogenic myxomas most common?

A
  • Most common in 3rd decade
  • F = M

(Mandible > maxilla)

30
Q

How do odontogenic myxomas present? (7)

A
  • Well-defined radiolucency +/- thin corticated margin
  • Smaller lesions unilocular and Larger lesions multilocular with scalloped margins
  • “Soap bubble” appearance
  • “Tennis racket” pattern of internal septa suggestive of myxoma but only occurs in minority of cases
  • Slow growth along bone before causing notable bucco-lingual expansion
  • Scallops between teeth but eventually as the lesions get larger = cause displacement
  • External root resorption rare
31
Q

Describe the histology of an odontogenic myxoma. (4)

A
  • Loose myxoid tissue (connective tissue) with stellate cells within
  • May contain islands of inactive odontogenic epithelium (vital but inactive)
  • No fibrous tissue capsule  locally invasive into adjacent bone and can cause problems with surgical removal and recurrence
  • Mesenchymal in origin
32
Q

Why are odontogenic myxomas recurrent?

A

No fibrous tissue capsule = locally invasive into adjacent bone and can cause problems with surgical removal and recurrence

33
Q

How do we manage odontogenic myxoma (2)

why is follow up important?

A
  • Curettage if small (scraped out) or resection if larger (block of bone taken away) - depending on sizes of the lesions

High recurrence rate: 25% = Follow-up important
(Lower recurrence rate if unilocular)

34
Q

What is an odontoma/odontome?

A

A Benign mixed “tumour” (Technically a hamartoma) from a malformation of dental tissue
- Enamel, dentine, cementum & pulp (don’t all have to be present

35
Q

In which ways are odontomes and teeth similar? (4)

A
  • Mature to a certain stage (do not grow indefinitely)
  • Can be associated with other odontogenic lesions (e.g. odontoma + dentigerous cysts)
  • Surrounded by dental follicle = radiolucent margin surrounding
  • Always lie above inferior alveolar canal
36
Q

In what age and in what sex are odontomas most common?

A
  • Most common in 2nd decade
  • F = M
37
Q

What are the 2 types of odontomes? (2)

How do these differ? (2)

A
  1. Compound odontoma
    - Ordered dental structures
    - May appear as multiple “mini teeth” (i.e. denticles)
    - More common in anterior maxilla
    Compound > complex (2:1)
  2. Complex odontoma
    - Disorganised mass of dental tissues
    - More common in posterior body of mandible
38
Q

Describe the histology of an odontome. (5)

A
  • Dental hard tissues present because odontomas originate from both types of epithelium and mesenchymal tissues
  • Dentine present
  • Soft tissue (resembles the tooth germ)
  • Areas that look like cementum
  • Enamel is an inorganic tissue structure – so enamel (if fully calcified) is dissolved during slide preparation and none is present
    Spaces can resemble where the enamel used to be

My BDS4 (57 decks)

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