L13 Odontogenic tumours Flashcards
Which tissue do odontogenic tumours arise from?
Epithelium within bone of the jaws
Describe the histological appearance of odontogenic tumours.
- Variable appearance due to pluripotent nature of odontogenic epithelium
- May resemble a developing tooth
- May contain dental hard tissues e.g. enamel, dentine, cementum
Are odontogenic tumours rare?
- Yes, all are rare
- Ameloblastoma is the most common odontogenic tumour type
How are benign odontogenic tumours classified?
3 categories:
- Odontogenic epithelium only (no odontogenic mesenchyme = no hard tissue)
- Mixed odontogenic epithelium (some, but not all, can develop hard tissue)
- Mesenchyme and/or odontogenic ectomesenchyme (can present with or without odontogenic epithelium, tend to be inactive)
Are odontomes actually true tumours?
No, they are developmental anomalies known as hamartomatous lesions.
Name the 4 odontogenic tumours with odontogenic epithelium only.
- Ameloblastoma
- Squamous odontogenic tumour
- Calcifying epithelial odontogenic tumour
- Adenomatoid odontogenic tumour
Describe the main features of ameloblastomas.
- Most common benign odontogenic tumour
- Odontogenic epithelium without odontogenic mesenchyme
- Locally invasive neoplasm
- 1% of oral tumours
- 3 common types: conventional (solid/multicystic), unicystic, peripheral
Where are ameloblastomas most common?
- 80% mandible, 20% maxilla
In the mandible: - 70% are in the molar region
- 20% premolar
- 10% incisor
What age are ameloblastomas most commonly seen in?
- 4th and 5th decades of life
What are the symptoms of an ameloblastoma?
- Slow growing so may be asymptomatic
- Gradually increasing facial deformity, expansion of the jaw
What are the signs of an ameloblastoma?
- Bony hard, non tender, ovoid swelling
- Egg shell crackling on palpation in advanced cases
- Perforation of bone and spread to soft tissues (late stage)
- In the maxilla large tumours may produce little swelling, mandibular tumours tend to present at a smaller size
Describe the radiographic features of an ameloblastoma.
- Mostly multicolular (soap bubble appearance), but unilocular when small
- Well defined, corticated outline
- Uniformly radiolucent with radiopaque septa
- Expansion of buccal/lingual bone
- Teeth displaced
- Roots of involved teeth may be resorbed
- Often associated in the mandible with unerupted 3rd molars and misdiagnosed as dentigerous cysts
How are ameloblastomas managed?
Surgical excision due to locally invasive nature.
Some even require segmental resection involving portions of the mandible if very large.
What are the 2 possible histological presentations of an ameloblastoma?
- Follicular pattern
- Plexiform pattern
Describe follicular-type ameloblastoma.
Histological description
- Discrete round islands or follicles
- Resemble the enamel organ of the tooth germ
- Central mass of loosely connected angular cells resembling stellate reticulum
- Peripheral layer of cuboidal or columnar cells resembling ameloblasts (with reverse polarity)
- Follicles are seperated by fibrous tissue
- Follicles may show cystic breakdown, squamous metaplasia (epithelium becomes squamous like) and granular cell change
What type of polarity do ameloblast cells in ameloblastomas exhibit?
Reverse polarity.
Nuclei at opposite end to BM.
Describe plexiform-type ameloblastoma.
- Tangled network of strands and irregular masses showing the same cell layers as the follicular pattern
- Peripheral layer of ameloblast-like columnar cells with central stellate reticulum like cells
Where do researchers beleive the epithlieum in ameloblastomas originates from?
- Dental lamina or glands of Serres thought to be most likely
Other theories include: - Enamel organ
- HERS or rests of Malassez
- Epithelial lining of odontogenic cysts
- Basal layer of oral epithelium
How are ameloblastomas treated?
Depends on type
For conventional ameloblastoma:
- Surgical resection with margin of normal bone
- High risk of recurrence after curettage (not used)
- Long term follow up, recurrence can occur up to 10 years post op
Describe the main features of adenomatoid odontogenic tumours.
- Odontogenic epithelium without odontogenic ectomesenchyme
- Duct-like structures
- May be parly cystic
- Slow growing
What type of patient is an adenomatoid odontogenic tumour most commonly seen in?
- 2nd or 3rd decades of life
- More common in women
Where are adenomatoid odontogenic tumours most commonly found?
- Maxilla twice more common than the mandible
- Anterior maxilla most common, especially in the canine area
Describe the radiographic features of adenomatoid odontogenic tumours.
What tumour does this image show?
An adenomatoid odontogenic tumour, note how it is attached to the entire tooth, not just the ACJ.
Describe the histopathology of adenomatoid odontogenic tumours.
- Well encapsulated
- Solid or partly cystic
- Sheets, strands and masses of epithelium
- May differentiate into ameloblast-like cells in places
- Columnar cells form duct-like structures! Unique diagnostic feature.
- No reverse polarity of columnar cells.
Describe the main features of calcifying epithelial odontogenic tumours.
Describe the radiographic presentation of an ameloblastic fibroma.
- Well defined radiolucency
- Usually unilocular (may be multilocular when larger)
- Well defined, corticated outline
- Uniformly radiolucent with radiopaque septa
Describe the histopathology of an ameloblastic fibroma.
- Proliferating strands and islands of odontogenic epithelium in a highly cellular fibroblastic stroma resembling the dental papilla of a developing tooth
- Epithelial component show peripheral layer of columnar or cuboidal ameloblast‐like cells enclosing small amounts of stellate reticulum like cells
- May be narrow cell‐free zone of hyaline connective tissue around epithelial component
Describe compound odontomes.
- Seen in the anterior maxilla most commonly
- Affects children
- Multiple tooth like structures
- 1-2cm in size
- Well organised enamel, dentine and pulp
Describe complex odontomes.
- < 20 years of age
- Posterior mandible
- Up to 3cm in size
- Impacts teeth or prevents eruption
- Spherical radiopaque mass
- Radiating peripheral radiopacities
- Radiolucent rim
- Haphazard dental structures
Describe the histopathology of a compound odontome.
- Separate denticles embedded in fibrous tissue
- Most denticles do not resemble normal teeth but in each one enamel, dentine, cementum and pulp arranged as in normal teeth
Describe the histopathology of a complex odontome.
- Mass of irregularly arranged but well formed enamel, dentine and cementum surrounded by a fibrous capsule
- Dentine forms bulk of lesion; pulp‐like tissue on surfaces not covered by enamel or cementum
Describe the radiographic features of a cementoblastoma.
- Well demarcated
- Mottled or dense radiopaque mass with radiolucent margin
- Attached to root of tooth which may show root resorption
Describe the histopathology of cementoblastomas.
- Mass of calcified cementum‐like tissue with many reversal lines
- Scattered cells in lacunae
- Uncalcified matrix at the periphery formed by
plump cementoblasts - Similar to osteoblastoma of bone
Describe odontogenic myxomas.
Describe the radiological presentation of odontogenic myxomas.
Uniformly radiolucent with radiopaque septa.
Multilocular.
Well defined, corticated outline.
