Odontogenic Tumours Flashcards
1
Q
What is a tumour
A
A swelling that includes malignant and benign neoplasms, hamartomas and some dysplasias
2
Q
Which tissues can neoplasms and other tumours of the jaw derive from and what does this mean?
A
- Can derive from odontogenic epithelium (dental lamina, reduced enamel epithelium, rests of Serres, rests of Malassez)
- No organised dental tissue can be formed due to no signalling from mesenchyme - Can derive from products of odontogenic mesenchyme (dental follicle, dental papilla, pdl)
- Or both
- Signalling from mesenchyme is present, tissue capable of producing dental hard tissue
3
Q
What is the simplified classification of Odontogenic tumours
A
- Benign epithelial tumours
- Ameloblastoma
- Calcifying epithelial odontogenic tumour (Pindborg Tumour)
- Adenomatoid odontogenic tumour - Benign mixed epithelial and mesenchymal tumours
- Ameloblastic fibroma
- Odontome (complex & compound)
- Calcifying odontogenic cyst (Dentinogenic ghost cell tumour) - Benign mesenchymal tumours
- Odontogenic fibroma
- Odontogenic myxoma/myxofibroma
- Cementoblastoma
4
Q
What features need to be taken into account when deciding what the lesion is?
A
- Age and sex of the patient
- Site or anatomical postion
- Size
- Shape - (unilocular/multilocular)
- Outline
- Relative radiodensitry and internal structure
- Effect on adjacent surrounding structures
- Time present - if possible
5
Q
Alternative reasons for similar radiopaque, mixed or radiolucent lesions
A
- Localised infection
- Spreading infection of bone (e.g. osteomyelitis)
- Trauma
- Cysts
- Tumours (non-odontogenic or odontogenic)
- Giant cell lesions
- Early stages of Fibro osseous lesions
- Idiopathic lesions
6
Q
What are the key features of an ameloblastoma
A
- Benign neoplasm of odontogenic epithelium
- Most common type and the most common neoplasm of the jaw
- Usually presents between 30-50yrs
- Most commonly forms in posterior mandible
- Symptomless until swelling is noticed (expansion may be both lingual and buccal)
- Ameloblastoma should be included in the differential diagnosis for nay radiolucency int he posterior alveolus and lower ramus of mandible
7
Q
What are the radiographic features of an ameloblastoma
A
- Rounded cyst-like, radiolucent areas with well-defined margins
- The smallest appear unilocular
- Larger ameloblastomas may comprise a few large clustered cysts (‘soap bubbled’ multi-locularity) or numerous small cysts a few mm across (‘honeycomb’ Multilocular pattern) or a mixture of patterns
- Other Multilocular lesions may mimic ameloblastoma radiographically: odontogenic keratocyst, giant-cell granuloma and Odontogenic myxoma
8
Q
What is the pathology of ameloblastomas
A
- Cause is unknown: V600E mutation activates MAP kinase pathway which drives cell division and differentiation
- They are a mixture of solid neoplasm and cysts, and either component may predominate
- Solid areas comprise fibrous tissue containing islands of interconnected strands and sheets of epithelium with a peripheral layer of palisaded preameloblast-like cells
1. Follicular type: isolated islands in connective tissue stroma
2. Plexiform: pattern of epithelium form interlacing strand of epithelial cells within sparsely cellular connective tissue (CT is in the islands) - Cyst formation is common, and there are usually several large cysts as large as a few cm in diameter
- Islands of ameloblastoma can extend into the medullary spaces of surrounding bone. Not expected in a benign neoplasm because it resembles infiltration by a malignant neoplasm. If left behind after surgery, it will seed recurrence
9
Q
Pooja what is the behaviour of ameloblasts?
A
- Enlarge the jaw slowly, displacing and often resorbing tooth roots, perforation the cortical bone and, if large, expanding into soft tissue constrained only by the periosteum (generally expands
- Although benign, it can be difficult to eradicate
- Maxillary ameloblastomas are particularly dangerous because bones are considerably thinner than the mandible. Can invade the cranium and brain and can be lethal
10
Q
What is the treatment of ameloblasts?
A
- Attempt to treat conservatively to avoid the morbidity of large surgical excisions, especially in adolescents - but case selection important and there may be recurrence. Small mandibular lesions can sometimes be enucleated, the cavity curated
- Typically tx: wide surgical excision, preferably removing 10mm of apparently normal bone around the margin to ensure that any extension into the medullary bone is removed
1. Complete excision of a large ameloblastoma may therefore require partial resection of the jaw, often with the condyle an bone grafting
2. Smaller lesions may be excised, leaving border of jaw intact
2. Bony repair then causes much of the jaw to re-form - Regular RAD follow up is essential
11
Q
What are the clinical features of a unicystic ameloblastoma?
A
- An ameloblastoa that has a single cyst cavity
- Present at a younger age than conventional ameloblastoma (20-30y)
- May account for 10% of all ameloblastomas
- May present in a true dentigerous relationship to an unerupted third molar (may simulate any odontogenic cyst but root resorption, cortical perforation or large size may give clues and if lesion attaches at CEJ then more confident of cyst)
- In theory, single cyst structure could mean that these could be treated by simple enucleation with low recurrence risk (as there is no extension into medullary bone) but preoperative diagnosis is difficult (can only tell unicystic from multicystic/solid conventional histologically) - often mistaken for a mural conventional ameloblastoma (which appears unicystic radiographically and requires excision not enucleation)
12
Q
What are the clinical features of Calcifying Epithelial Odontogenic Tumour (Pindborg Tumour)
A
- Rare neoplasm of odontogenic epithelium (benign)
- Usually presents between 40-70y
- Most commonly forms in posterior mandible
- Solid tumour
- Well defined radiolucent initially, becoming mixed radiolucency with time (increasing radiopacity when it mineralises)
- Histopathology can resemble carcinoma
- The only odontogenic tumour to contain amyloid (in CT; secreted by epithelial cells; mineralises)
- Locally infiltrative like ameloblastoma
- Treated by excision with small margin
13
Q
Radiology of CEOT (Pindborg tumour)
A
- Site: posterior of mandible, occasionally in maxilla
- Size: tend to remain small
- Shape: unilocular or multilocular
- Outline: Variable but generally well defined and corticated
- Relative radiolucency: Early lesions radiolucent but as tumour matures and calcifies can have areas of varying radiolucency
- Effects on adjacent structures: Expands buccal bone
- Differential diagnosis: Dentigerious cyst (distinguished by calcifications), odontomes
14
Q
Radiology of unicystic ameloblastoma
A
- Site: posterior of mandible
- Size: several CM
- Shape: unilocular
- Outline: well defined and corticated
- Relative radiolucency: radiolucent
- Effects on adjacent structures: Displaces teeth, expands bone, resorbs roots
15
Q
Radiology of multicystic ameloblastoma
A
- Site: posterior of mandible
- Size: Several CM
- Shape: multilocular
- Outline: well defined and corticated
- Relative radiolucency: Radiolucent
- Effects on adjacent structures: Expands bone, resorbs roots, displaces teeth
- Differential diagnosis: Odontogenic keratocyst (but OKCs do not displace teeth)
