Odontogenic Tumours

Question 1

Are they rare

Answer 1

Yes

1% of oral & maxillofacial lesions sent for histopathological assessment in UK

Question 2

What non-cystic radiolucent lesions are there

Answer 2

Odontogenic tumours
-Amrloblastoma
-Ameloblastic fibroma
-Malignant ameloblastoma
-Odontogenic fibroma and myxoma

Giant cell lesions
-Peripherla and central giant cell granuloma
-Brown tumours of hyperparathyroid
-Cherubism

Fibro cemento osseous lesions

Radiolucent non-odontogenic tumours
-Chondroma
-Osteosarcoma
-Squamous cell carcinoma

Question 3

Are they more bengin or malignant

Answer 3

Benign&raquo_space; malignant (100:1)

Question 4

What are the symptoms

Answer 4

Majority asymptomatic and discovered due to late eruption of teeth, late stage bony expansion or imaging for ther reasons

Question 5

Where do they arrise

Answer 5

Mostly within bone of jaws

Question 6

Whatare the classifications

Answer 6

Grouped based on there tissue of origin

-Epithelial

-Mesenchymal

-Mixed (only tumour to have dentine/enamel formation)

Question 7

What are the odontogenic sources of epithelium of odontogenic tumours

Answer 7

Rests of Malassez
-Remnants of Hertwig’s epithelial root sheath

Rests of Serres
-Remnants of the dental lamina

Reduced enamel epithelium
-Remnants of the enamel organ

Question 8

What is meant by the concept of induction

Answer 8

cannot have enamel without dentine

Odontoblasts forms dentine (mesenchymal origin) ameloblasts only start to form enamel once dentine is layed down, So the presence of dentine is important for induction of maturation of ameloblasts and then formation of enamel

Question 9

What forms hertwigs epithelial root sheath

Answer 9

inner and outer odontogenic epithelium (on histology side its the bits forming the roots)

Question 10

What forms the tooth germ

Answer 10

Dental lamina

Question 11

Give examples of epithelial, mesenchymal and mixed tomours

Answer 11

Epithelial
-Ameloblastoma
-Adenomatoid odontogenic tumour
-Calcifying epithelial odontogenic tumour

Mesenchymal
-Odontogenic myxoma

Mixed
-odontoma

Question 12

What are the radiographic features of a odontogenic tomour

Answer 12

Highly variable

Question 13

> 50% of cases are either what

Answer 13

ameloblastoma or odontoma

Question 14

What is a ameloblastoma and what is the incidence

Answer 14

Benign epithelial tumour
-Locally destructive but slow-growing
-Typically painless

inidence
-1% of oral & maxillofacial tumours
-Most common in 4th-6
the decades
-80% occur in posterior mandible
-M > F

Question 15

What are the radiologically types of ameloblastomas

Answer 15

Multicystic (85-90%)

Unicystic

Question 16

What are the histological types of ameloblastomas

Answer 16

Follicular

Plexiform

Desmoplastic

Question 17

What are the radiograhpic features of a ameloblastoma

Answer 17

Margins
-Well-defined, corticated
-Potentially scalloped

Multicystic type
-May have thick, curved septa → “soap bubble” appearance

Primarily radiolucent

Adjacent structures
-Displacement
-Thinning of bony cortices
-“Knife edge” external root resorption

Question 18

What is the histology of a follicular ameloblastoma

Answer 18

Islands with ameloblast like cells lining them with a fibrous tissue background

Ameloblast-like cells

Stellate reticulum like tissue, in the inside of the islands

Fibrous tissue

Cystic changes in the island

Question 19

What is the histology of plxiform ameloblastoma

Answer 19

Ameloblast-like cells arranged in strands sometimes with stellate reticulum like tissue inbetween

Stellate reticulum like tissue

Fibrous tissue

Question 20

What is the key thing about ameloblastomas and what does it result in

Answer 20

No Connective tissue capsule

Cells wont be stopped gorwing and infiltrating into jaw bone resulting in the high recurrence rate

Question 21

What is the mangement of ameloblastomas

Answer 21

Surgical resection with margin

Recurrence relatively common, Up to 15% of cases

Question 22

Risk of malignant transformation of ameloblastoma

Answer 22

<1% of cases

Ameloblastic carcinoma

Question 23

What is a Adenomatoid odontogenic tumour (AOT) and what is its incidence

Answer 23

Benign epithelial tumour

Incidence
-3% of odontogenic tumours
- 2nd decade
-F > M
-Majority occur in anterior maxilla

Question 24

What is the presentation of AOT

Answer 24

75% associated with an unerupted toothCommonly a maxillary canine
-Similar to dentigerous cyst but typically attached apical to cemento-enamel junction
-Impedes eruption

Unilocular radiolucency

Majority have internal calcifications/radiopacities

Margins well-defined & corticated/sclerotic

May displace adjacent structures but external root resorption is rare

asymmetrical

Question 25

What is the histology of a AOT

Answer 25

Epithelial cells can present as a duct like structure or have a rosette apperance Some calcification leading to distinctive patches Well developed fibrous tissue capsule

Question 26

What is a Calcifying epithelial odontogenic tumour (CEOT) and what is its incidence

Answer 26

A benign epithelial tumour (Pindborg tumour) Incidence -1% of odontogenic tumours -5th decade -M > F -Posterior mandible is most common site

Question 27

What is the prsentation of CEOT

Answer 27

Slow-growing but can become large Half associated with 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

Question 28

What is a Odontogenic myxoma and its incidence

Answer 28

Benign mesenchymal tumour Incidence -3-6% of odontogenic tumours -3rd decade -F = M -Mandible > maxilla

Question 29

What is the presentation of odontogenix myxoma

Answer 29

Well-defined radiolucency +/- thin corticated margin Smaller lesions unilocular Larger lesions multilocular with scalloped margins -“Soap bubble” appearance Slow growth along bone before causing notable bucco-lingual expansion Scallops between teeth but larger lesions may cause displacement External root resorption rare

Question 30

What is the histology of a odontogenic myxoma

Answer 30

Loose myxoid tissue with stellate cells May have smalls groups of odontogenic epithelium May contain islands of inactive odontogenic epithelium No capsule → locally invasive into adjacent bone

Question 31

What is the management of odontogenic myxoma

Answer 31

Curettage or resection High recurrence rate: 25% -Follow-up important -Lower recurrence rate if unilocular

Question 32

What is a odontoma and what is its incidence

Answer 32

Benign mixed “tumour” -Technically a hamartoma Malformation of dental tissue -Enamel, dentine, cementum & pulp Similarities to teeth -Mature to a certain stage -Can be associated with other odontogenic lesions (e.g. dentigerous cysts) -Surrounded by dental follicle Lie above inferior alveolar canal Incidence -1/5 to 2/3’s of all odontogenic tumours -2nd decade -F = M

Question 33

What are the types of odontoma

Answer 33

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

Question 34

What is the histology of a odontoma

Answer 34

Will have dental hard tissues -Dentine and enamel space(as enamel inorganic so it get dissolved in prep)

Question 35

What is mainly used for treating ameloblastoma and sarcoma and what ha[[ens

Answer 35

Segmental resection: -Removal of cyst with margin of ‘normal’ bone -Normally require secondary procedure for reconstruction of defect