odontogenic tumours

Question 1

occurence of odontogenic tumours

Answer 1

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

Benign&raquo_space; malignant (100:1)

Majority asymptomatic
* Often discovered due to non-eruption of teeth, late-stage bony expansion or imaging for other reasons (i.e. incidental)
* Pain usually secondary to infection or pathological fracture

Mostly arise within the bone of the jaws
* Rare cases can be within the surrounding soft tissue

Question 2

classification of odontogenic tumours

3 groups

Answer 2

epithelial
mesenchymal
mixed (epithelium and mesenchymal)

based on germ cell layer of tissue origin

Question 3

which class of odontogenic tumour can have enamel/dentine formation

Answer 3

only mixed tumours

due to concept of induction
* means that formation of dental hard tissues in the tumours needs the presence of both types of tissues.
* Dentin formation (mesenchymal in origin) will induce maturation of ameloblasts and the formation of enamel (epithelial in origin).
In the other two groups, the tumour originates from one kind of tissue only so there is no hard tissue formation

Question 4

3 odontogenic sources of epithelium

Answer 4

rests of malassez
rests of serres
reduced enamel epithelium

Question 5

rests of malassez

Answer 5

Remnants of Hertwig’s epithelial root sheath (remnants of both inner and outer odontogenic epithelium; forms the outline of the hard tissues of the root)

Question 6

rests of serres

Answer 6

Remnants of the dental lamina (responsible for the formation of the tooth germs – after tooth formation has ceased, DL will breakdown leaving small clumps of cells remaining)

Question 7

reduced enamel epithelium

Answer 7

Remnants of the enamel organ (after crown formation complete; outer and inner enamel epithelium become close to each other and stellate reticulum covers the crown of the unerupted tooth?)

Question 8

3 examples of epithelial odontogenic tumours

Answer 8

ameloblastoma
adenomatoid odontogenic tuumour
calcifying epithelial odontogenci tumour

Question 9

example of mesenchymal odontogenic tumour

Answer 9

odontogenic myxoma

Question 10

example of mixed odontogenic tumour

Answer 10

odontoma

Question 11

‘-oma’ indicates

Answer 11

neoplasm

Question 12

radiographic appearance of odontogenic tumour

Answer 12

Entirely radiolucent ↔ mixed ↔ entirely radiopaque
* May change as tumour progresses

> 50% of cases are either ameloblastoma or odontoma
* Debate over which is most common (due to issues with data collection & overall scarcity)
* Ameloblastoma often stated as more common but studies are based on histopathology results – odontomas arguably not often sent for histopathological assessment

Question 13

what are ameloblastomas

Answer 13

Benign epithelial tumour

Locally destructive but slow-growing – cause damage locally

Typically painless

Question 14

incidence of amleoblastomas

Answer 14

1% of oral & maxillofacial tumours
Most common in 30-60y
80% occur in posterior mandible
M > F

Question 15

types of ameloblastoma

2 categories with subgroups

Answer 15

Radiological
* Multicystic (85-90%)
* Unicystic - Younger patients;Lower recurrence risk

Histological
* Follicular
* Plexiform
* Desmoplastic (more radiopaque than other typical ameloblastomas)
(Several other less common types)

Question 16

radiographic characteristics of ameloblastomas

Answer 16

Margins
* Well-defined, corticated
* Potentially scalloped (undulating margin – only seen in multicytic type)

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

Primarily radiolucent (but rare variants can be mostly radiopaque e.g. desmoplatic, sometimes if there is many septa can appear radiopaque)

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

characteristic pattern of expansion – expand in all direction equally
unlike odontogenic keratocyst – along the bone before buccal lingual expansion

Question 17

radiological classifications of ameloblastoma

Answer 17

multicystic 85-90%
unicystic (younger pt, lower recurrence risk)

Question 18

histologica classifications of ameloblastomas

3

Answer 18

Follicular
Plexiform
Desmoplastic (more radiopaque than other typical ameloblastomas)

(Several other less common types)

Question 19

histologica classifications of ameloblastomas

3

Answer 19

Follicular
Plexiform
Desmoplastic (more radiopaque than other typical ameloblastomas)

(Several other less common types)

Question 20

follicular ameloblastoma histology characteristics

4

Answer 20

Islands present in fibrous tissue background

Bordered by columnar cells with darkly staining nuclei (resemble ameloblast)

In middle of follicle – loose tissue, resembling the stellate reticulum of the tooth germ

Can have cystic changes within the tooth germ – varying sizes

Question 21

plexiform ameloblastoma histology characterics

4

Answer 21

Same basic histology as the follicular

Arranged differently
* Ameloblastoma-like cells arranged in strands
* Stellate reticulum like tissue in between strands
* Can be back-back ameloblastoma-like cells with no stellate reticulum like in between
* Supported by fibrous tissue

Question 22

plexiform ameloblastoma histology characterics

4

Answer 22

Same basic histology as the follicular

Arranged differently
* Ameloblastoma-like cells arranged in strands
* Stellate reticulum like tissue in between strands
* Can be back-back ameloblastoma-like cells with no stellate reticulum like in between
* Supported by fibrous tissue

Question 23

key histological features of ameloblastomas

Answer 23

No connective tissue capsule in any ameloblastomas – means the tissue can infiltrate into jaw bone - high recurrence rate

Question 24

describe this clinical case

16yo female with lump on lower jaw
* Present for some months
* Occasional pain initially but none now
* Gradually getting bigger

Clinical examination
* Hard, bony swelling located buccal to teeth 35-37
* Teeth not TTP
* Partially-erupted 38

Answer 24

Well defined corticated margins
Septae within
Thinning of inferior corticated margin of the mandible
Knife edge root resorption of the distal and mesial root of 36
Displacement of IDC

Question 25

management of ameloblastoma

Answer 25

**Surgical resection with margin (1cm of normal bone – prevent recurrence)** Recurrence relatively common * Up to 15% of cases Risk of malignant transformation * <1% of cases * Ameloblastic carcinoma

Question 26

what is adenomatoid odontogenic tumour (AOT)

Answer 26

Benign epithelial tumour “Unilocular radiolucency with internal calcifications around crown of unerupted maxillary canine” is classic presentation

Question 27

incidence of adenomatoid odontogenic tumour (AOT)

Answer 27

3% of odontogenic tumours Most common in 10-20y F > M Majority occur in anterior maxilla 75% associated with an unerupted tooth * Commonly a maxillary canine * Similar to dentigerous cyst but typically attached apical to cemento-enamel junction * Impedes eruption

Question 28

radiographic characteristics of adenomatoid odontogenic tumour

Answer 28

similar to dentigerous cyst but typically attached apical to CEJ Unilocular radiolucency Majority have internal calcifications/radiopacities * Increase as tumour matures Margins well-defined & corticated/sclerotic (thick unlike others) May displace adjacent structures but external root resorption is rare

Question 29

histology of adenomatoid odontogenic tumour

Answer 29

epithelial origin – arranged in duct like structures or sheets or rosette appearance some calcification (seen in radiograph) well developed fibrous tissue capsule surrounding the AOT - removal easier and recurrence low

Question 30

describe this case RFA - delayed eruption 33

Answer 30

radiolucent area around crown of 33 – bulges out around mesial aspect root – well defined corticated radiolucency, not symmetrical (rules our follicle or dentigerous cysts), **involving root and crown - AOT** Tooth needs aid to erupt

Question 31

what are calcifying odontogenic tumours (CEOT)

Answer 31

Benign epithelial tumour a.k.a. Pindborg tumour Incidence * 1% of odontogenic tumours * Most common in 5th decade * M > F * Posterior mandible is most common site

Question 32

most common odontogenic tumours

Answer 32

ameloblastomas or odontomas (>50%) | odontomas the most common

Question 33

incidence of calcifying epithelial odontogenic tumours (CEOT)

Answer 33

* 1% of odontogenic tumours * Most common in 5th decade * M > F * Posterior mandible is most common site

Question 34

presentation of calcifying epithelial odontogenic tumours

Answer 34

Slow-growing but can become large Half are associated with an 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 Hard to dx

Question 35

what are odontogenic myxomas

Answer 35

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

Question 36

incidence of odontogenic myxomas

Answer 36

* 3-6% of odontogenic tumours * Most common in 3rd decade * F = M * Mandible > maxilla

Question 37

presentation of odontogenic myxomas

Answer 37

Well-defined radiolucency +/- thin corticated margin * Smaller lesions - unilocular * Larger lesions multilocular with scalloped margins “Soap bubble” appearance “Tennis racket” pattern of *internal septa* suggestive of myxoma but only occurs in minority of cases Slow growth along bone before causing notable bucco-lingual expansion Scallops between teeth but larger lesions may cause displacement * External root resorption rare

Question 38

histology of odontgenic myxoma

Answer 38

* Loose myxoid tissue with stellate cells * May contain islands of inactive odontogenic epithelium * No capsule so locally invasive mesenchymal in origin

Question 39

management of odotogenic myxoma

Answer 39

Curettage or resection (depending on size) High recurrence rate: 25% * Follow-up important * Lower recurrence rate if unilocular

Question 40

what are odontomes

Answer 40

**benign mixed 'tumour'** Technically a hamartoma *not technically a neoplasm* **Malformation of dental tissue * Enamel, dentine, cementum & pulp** Similarities to teeth * Mature to a certain stage (i.e. do not grow indefinitely) * Can be associated with other odontogenic lesions (e.g. dentigerous cysts) * Surrounded by dental follicle * Lie above inferior alveolar canal can cause impaction of teeth | aka odontoma ortho calls them supernumeraries

Question 41

incidence of odontomes

Answer 41

1/5 to 2/3’s of all odontogenic tumours Most common in 2nd decade F = M

Question 42

2 types of odontomes

Answer 42

compound complex | Compound > complex (2:1)

Question 43

compound odontome

Answer 43

Ordered dental structures * May appear as multiple “mini teeth” (i.e. denticles) More common in anterior maxilla

Question 44

complex odontome

Answer 44

Disorganised mass of dental tissues More common in posterior body of mandible

Question 45

what is the more common type of odontome

Answer 45

Compound > complex (2:1)

Question 46

histology of odontome

Answer 46

Has dental hard tissue – originates from both epithelial and mesenchymal tissues Dentine seen Enamel is dissolved in slide preparation if fully calcified – spaces where it was (inorganic, if not fully calcified will have some organic substance left and can be seen)