Odontogenic Tumours Flashcards
What are the general features of Odontogenic tumours?
Benign: Malignant is 100 to 1
Rare
Mostly asymptomatic
-> found as incidental finding when imaging for impacted teeth or caries
Mostly arise within bones of teeth
-> can sometimes be within soft tissue
When may pain occur from odontogenic tumours?
Secondary to infection
If tumour has caused pathological bone fracture
What are the different classifications of Odontogenic tumours?
Epithelial
Mesenchymal
Mixed- only these can contain dentine AND enamel
What is the concept of induction in enamel formation?
First hard tissue formed is dentine from odontoblasts (mesenchymal origin)
Ameloblasts form enamel only when dentine has already been started
-> Presence of dentine is important in triggering maturation of ameloblasts and then starting to form enamel
What are the epithelial sources of odontogenic tumours? (same as cysts)
Rests of Malassez
-> Remnants of Hertwig’s epithelial root sheath
Rests/glands of Serres
-> Remnants of the dental lamina
Reduced enamel epithelium
-> Remnants of the enamel organ
How do rests of malassez form?
HERS forms from inner and outer odontogenic epithelium
-> HERS forms outline and hard tissues of the root- once this is completed the epithelium breaks down
-> Remnants of HERS can stay as clumps of inactive cells in PDL (vital but don’t divide)
How do rests of Serres form?
Dental lamina (responsible for formation of tooth germ) can break down and clumps of cells can persist
What is the reduced enamel epithelium?
Formed after crown has formed
-> OEE and IEE come close and stellate reticulum disappears and covers crown of unerupted tooth
What are examples of the different types of odontogenic tumours?
Epithelial
-> Ameloblastoma
-> Adenomatoid Odontogenic Tumour
-> Calcifying Epithelial Odontogenic Tumour
Mesenchymal- Odontogenic Myxoma
Mixed- Odontoma
What re the most common odontogenic tumours?
Ameloblastoma OR Odontoma account for 50% of all OT
-> debate which is most common as odontomas have classic appearance and may not be sent for histopathological assessment
What can make Odontogenic tumours difficult to diagnose on radiographs?
Appearance can be variable and change as they mature
What are the features of Ameloblastoma?
Benign
Slow growing
Locally destructive
Typically painless
What are the epidemiological features of Ameloblastoma?
1% of oral & maxillofacial tumours
Most common in 4th-6th decades
80% occur in posterior mandible
M >F
What are the types of Ameloblastoma?
Radiology:
Multicystic- more common
Unicystic- single unilocular radiolucency (lower recurrence risk)
Histology:
Follicular
Plexiform
Desmoplastic- appears more radiopaque
What are the radiographic features of Ameloblastoma?
- Well defined
- Corticated
- Scalloped margins- undulating (not seen in unicystic)
- In multi-cystic- large bony septae seen through lesion (soap bubble appearance)
- Primarily radiolucent
- Displacement of teeth and IAC
- Thinning of cortices- seen in aggressive form
- Knife edge external root resorption- clean cut resorptive lesion (not ragged)
How does expansion of Ameloblastoma differ from an Odontogenic keratocyst?
Ameloblastoma expands in all directions equally
-> OK tends to expand along bone bucco-lingually
What are the histological features of Follicular Ameloblastoma?
- Islands present within fibrous tissue background, bordered by cells resembling ameloblasts (columnar cells, dark stained nucleus)
- Tissue in middle of follicles- loose tissue similar to stellate reticulum (may be cystic changes or squamous metaplasia within follicles)
What are the histological features of Plexiform Ameloblastoma?
- Similar to follicular but different arrangement
- Ameloblast like cells arranged in strands with stellate reticulum like tissue between
- Fibrous tissue support
How can ameloblastoma be differentiated from bony swelling caused by abscess?
Teeth in vicinity are not painful or TTP
How are Ameloblastomas managed?
Surgical resection with margin
- 1cm of healthy bone taken away to help prevent recurrence
- Can be large
- Would require bone grafts and metal plates
What is the likelihood that an Ameloblastoma will reoccur?
15%
What happens when an Ameloblastoma undergoes malignant transformation?
It forms a Ameloblastic Carcinoma (<1% of cases)
What is the issue with early detection of Ameloblastomas?
It is difficult as the lesions are small and easily missed
What is the classic presentation of Adenomatoid Odontogenic tumour?
Unilocular radiolucency with internal calcifications around crown of
unerupted maxillary canine
