Odontigenic tumours of the jaws

Question 1

What is the classification?

Answer 1

WHO 2017 1. BENIGN A. Epithelial derived - Ameloblastoma (86%) - unicystic 13% or classical - clarifying epithelial odontigenic tumour -Adenomatoid odontigenic tumour B. Mixed derived (mes and epi) - Ameloblastic fibroma - odontoma (compound/supernumary, complex/dens) C. Mesenchymal origin - odontogenic myoxoma/myomixfibroma - cementoblastoma - cementoossifying fibroma 2. MALIGNANT - Odontogenic carcinoma (Ameloblastic carcinoma)

Question 2

What is an ameloblastoma?

Answer 2

benign epithelial derived odontogenic tumour, second most common odontogenic tumour. -slow growing locally invasive growth from dental lamina, enamel organ and basal cells of the oral mucosa. B/L expansion. -Genes hedgehog, MAPK

Question 3

How does ameloblastoma present?

Answer 3

-30-40s, angle of mandible -unilocular (13%) or multilocular (classic) -soap bubble appearance with root resorption

Question 4

What’s the histological presentation of Classic ameloblastomas?

Answer 4

-Solid tumour with islands of cystic changes

There are 6 subtypes:

1. Follicular pattern- common. epithelial islands, loose stellate reticulum with columnar ameloblasts (with reverse polarity). the islands resemble enamel organ with cystic changes
2. Plexiform pattern- long anastomosing chords of columnar like cells, stroma lose and vascular, cyst uncommon
3. Acanthomatous 4. Granular cell 5. Basal cell 6. Desmoplastic

Question 5

What is the presentation of unicystic ameloblastoma?

Answer 5

-younger patients (20s), posterior mandible (38/48) impacted/unerupted, asymptomatic and well circumscribed unilocular radiolecency.

Question 6

What are the 3 variants of unicystic ameloblastoma?

Answer 6

1. Luminal: confined to luminal surface of the cyst with fibrous wall of ameloblastic epithelium 2. intraluminal: 1 or more nodules of lining projections 3. Mural: follicular of flexiform infiltration. pseudomulti

Question 7

How is ameloblastoma treated?

Answer 7

Luminal/intra: decompression/marsuplisation if large then enucleation is successful Mural/conventional: resection due to infiltrate has higher re-occurance rate BDJ Ghandi 06

Question 8

What is an adenomatoid odontogenic tumour?

Answer 8

Benign Epithelial derived odontogenic tumour. -2-7% of odontogenic tumours. usually asymptomatic -tumour of 2/3rds. F, max canines, 20s.

Question 9

What is the radiographic appearance of an adenomatoid odontogenic tumour?

Answer 9

-circumscribed radiolucent unilocular lesion surrounding the crown of an unerupted tooth. -may have snowflake calcifictions

Question 10

What is the histological appearance of an adenomatoid odontogenic tumour?

Answer 10

thick fibrous capsule -epithelial cells for rosette structure in central space -looks glandular but not -may have amyloid and calcifications

Question 11

How is an adenomatoid odontogenic tumour treated?

Answer 11

Surgical enucleation and curettage, reoccurrence uncommon

Question 12

What is a pinborg tumour (calcifying epithelial odontogenic tumour)?

Answer 12

uncommon 1%, asymptomatic, posterior mandible. slow growing. -PTCH mutation -30-50s.

Question 13

What is the radiographic appearance of a pinborg tumour (calcifying epithelial odontogenic tumour)?

Answer 13

unilocular with scalloped margins -may be well defined, mixed with snow like expasions around impacted teeth

Question 14

What is the histological appearance of a pinborg tumour (calcifying epithelial odontogenic tumour)?

Answer 14

prominent desmosomes with areas of calcification in fibrous stroma. calcifications form centric rings and then fuse to form complex masses -nuclear pleomorphism -stains green with congo red stain.

Question 15

How are pinborg tumour (calcifying epithelial odontogenic tumour) treated?

Answer 15

enucleation and debridement of bone rim, 15% reoccurance rate

Question 16

What are the two main types of mixed benign odontogenic tumours?

Answer 16

• ameloblastic fibroma - Odontoma

Question 17

What is an Ameloblastic fibroma?

Answer 17

a benign mesenchymal (dental papilla) origin and epithelial origin (lamina) odontogenic tumour -20s, males, larger lesion have swelling, 70% posterior mandible. - Radio: uni or multi, well corticated on unerupted tooth -Histo: may have capsule. solid tumour of papilla like structure with epithelial chords (cub or columnar) -tx; excision and peripheral ostectomy, 18% reoccurance

Question 18

What is an odontoma? (garvey)

Answer 18

most common mixed odontogenic benign tumour. -dental hamartoma, meaning that it is composed of normal dental tissue that has grown in an irregular way. epithelial and mesenchyme origins 2 variants: 1. Compound (supernumerary) 2. Complex (dens invaginatus)

Question 19

What is a compound odontoma

Answer 19

more frequent, sumpernumary teeth -due to extra budding and proliferation of the dental lamina -detected in under 20s usually due to ectopic/delayed eruption . most common anterior maxilla (mesiodens) -histologically tooth structure, may be morphologically different -Tx; leave and review, removal. risk of cystic development (2, 5 yr follow ups), may cause resorption of other teeth.

Question 20

What is a complex odontome?

Answer 20

infolding of tooth germ, does not remsemble a tooth but contains lamina and papilla remnants (epithelial and mesenchymal)

• <20, asymptomatic, molar region
• histologically appears as mature dentine and enamel clefts, epithelial ghost cells
• 20% has epithelium that has keratinised and become necrotic
• may have dentigerous cyst involvement
• Tx: excison if symptomatic

Question 21

Wht are the benign mesenchymal odontogenic tumours?

Answer 21

1. odonotogen myxoma/myxofibroma
2. cementoblastoma
3. cementoossifying fibroma

Question 22

What is an odonotogenic myxoma?

Answer 22

arises from odontogenic mesenchyme

• 20-30years, posterior mandible
• B expansion when larger but asymptomatic
• scalloped margins with soup bubble appearance
• displaces and resorbs roots
• right angled trabecular

Histology: myxoid stroma containing stallate/spindle cells (hydranonic acid) may have cementum liek calcification

-tx: resection due to infiltration, not capsulated - 28%

Question 23

What is a cementoblastoma?

Answer 23

benign mesenchymal odontogenic tumour

• young adults and children, 1%
• 75% in mandible, pain and swelling occurs

Radiographically: radioopaque mass fused to root with radiolucent halo present. Root resorption and fusion

Histological: thick sheets of trabecular mineralised with interseptal lucana and basophilic reverse line. Fibrovascular CT

• atypical giant cells
• Tx: exo with lesion

Question 24

What is a cemento ossifying fibroma?

Answer 24

• benign fibro osseous lesion
• 30/40s, female, mandible, premolars/molars
• invades antrum, asymmetry and deformity
• radiographic: expansive well corticated unilocular mixed radiolucency somtimes also with halp
• displaced and resorbs roots, B/L expansion

Histology: capsulated well demarcated, blends into CT.

Tx: large resection, or enulceation with ostectomy. 12%

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Question 25

What is a malignant odontogenic tumour?

Answer 25

Ameolbasltic carcinoma -similar to ameloblastoma characterisitcs, can be primary or met -- increased cytopleomirphism - nuclear hyperchromatism - mitotic - necoritc islands. - aggressive, 60+ in men, BRAF mutation - well defined margins with cortical destruction and extends into soft tissue