Odontogenic tumours

Question 1

What are odontogenic tumours?

Answer 1

 Tumours of dental tissues

 Can be solid or cystic or mixed

• They can consist of odontogenic epithelium, ectomesenchyme or both.
• They are relatively rare.

Question 2

What classifies as odontogenic epithelium?

Answer 2

 Enamel organ

 Remnants of dental lamina (Rests of Serres)

 Hertwigs root sheath (Malassez)

Question 3

What classifies as ectomesenchyme?

Answer 3

 Dental papilla

 Dental follicle

Question 4

What is the WHO classification of odontogenic tumours?

Answer 4

 MALIGNANT:

• Carcinoma
• Sarcoma

 BENIGN:

• Epithelium without ectomesenchyme
• Epithelium with ectomesenchyme
• Mesenchyme and/or ectomesenchyme +/- epithelium
• Bone related

 OTHERS:

-Melanotic neuroectodermal tumour infancy

Question 5

What is an Odontogenic epithelium without ectomesenchyme?

Answer 5

A benign odontogenic tumour. eg:

• Ameloblastoma + variants: Solid, Peripheral, Desmoplastic, Unicystic, Acanthomatous
• Squamous Odontogenic tumour
• Calcifying epithelial odontogenic tumour (CEOT)
• Adenomatoid Odontogenic Tumour

Question 6

What are the most common odontogenic tumours?

Answer 6

• Odontomes (75%)
• Ameloblastomas (12%)
• Odontogenic myxoma
• Adenomatoid odontogenic tumour
• Ameloblastic fibro-odontoma
• Ameloblastic fibroma
• Calcifying odontogenic cyst
• Odontogenic fibroma

Question 7

What are odontomes?

Answer 7

• The most common type of odontogenic tumour
• Tumour- like lesions consisting of mature calcified dental tissues
• You can get complex or compound odontomes

Question 8

What is a complex odontome?

Answer 8

 Irregular mass of enamel, dentine, cementum and connective tissue

 Encapsulated, usually single

 Molar/premolar region

Clinical complications:

 Replaces tooth of normal series

 Impedes eruption of other teeth

 Expands bone

 Cystic change

 When it erupts can cause secondary infection and pain

Question 9

What is a compound odontome?

Answer 9

 Collection of small tooth-like structures (denticles)

 Intercanine region, especially maxilla

 Distinction from complex odontome is arbitrary - hybrid variants are common

Question 10

What is an ameloblastoma?

Answer 10

• Example of epithelial tumour
• Less than 1% of oral tumours
• Mean age 40 years
• Slow growing, locally invasive, painless bone expansion, root resorption
• 80% mandible:
• angle
• symphysis (Africans)

• Rare extra-osseous (peripheral) variants

Question 11

How does an ameloblastoma look on a radiograph?

Answer 11

• Multilocular cystic radiolucency
• +- expansion
• +- root resorption
• Occasionally unilocular/unicystic
• ? dentigerous variants

Question 12

What is a unicystic ameloblastoma?

Answer 12

Accounts for ~15% of Ameloblastoma. Equal distribution between maxilla and mandible. Usually unilocular associated with the crown of an un erupted tooth peak age 35 years.

 Single cyst

 90% mandible

 80% unerupted tooth

 Luminal

 Intraluminal

 Mural

Question 13

What are the microscopal features of an ameloblastoma?

Answer 13

• Thought to arise from cell rests of Serres
• Ameloblast-like cells surround stellate cells follicular plexiform

Question 14

What is an ameloblastic fibroma?

Answer 14

• Epithelial tumour with ectomesenchyme
• Most patients below 20 years
• Mandibular molar/premolar region
• Well defined, usually unilocular radiolucency
• Radiopacities in ameloblastic fibro- dentinoma (fibro-odontome)

Question 15

What is the microscopy of an ameloblastic fibroma?

Answer 15

• Odontogenic epithelium
• Cellular fibroblastic stroma
• With or without inductive changes:
• ameloblastic fibrodentinoma
• ameloblastic fibro-odontome

Question 16

What is an odontogenic myxoma?

Answer 16

Mesenchymal tumour

Painless swelling of either jaw

Children or young adults

Soap-bubble radiolucency

Unerupted or missing tooth common

 Microscopy:

• scanty stellate cells
• mucoid stroma +- fibrous tissue
• +-odontogenic rests
• widespread bony infiltration