6. Odontogenic Tumors

Ameloblastoma - plexiform patternAmeloblastoma - follicular patternAmeloblastoma - plexiform pattern6. Odontogenic tumours August 1, 2025 8:19 AM

Oral Pathology module

WHO Classification of Odontogenic Tumours (Kramer et al 1991)

• based on the similarity between tumours and various stages of tooth development

Classification of Benign Odontogenic Tumours

• Odontogenic epithelium without odontogenic ectomesenchyme
• Odontogenic epithelium with odontogenic ectomesenchyme, with or without dental hard tissue formation
• Odontogenic ectomesenchyme with or without included odontogenic epithelium

Odontogenic Tumour Classification Details

1. Odontogenic epithelium without odontogenic ectomesenchyme

• Ameloblastoma
• Squamous odontogenic tumour
• Adenomatoid odontogenic tumour
• Calcifying epithelial odontogenic tumour (Pindborg Tumour)

2. Odontogenic epithelium with odontogenic ectomesenchyme with or without dental hard tissue

• Ameloblastic fibroma
• Ameloblastic fibro-dentinoma
• Ameloblastic fibro-odontome
• Calcifying odontogenic cyst
• Complex odontome
• Compound odontome

3. Odontogenic ectomesenchyme with or without included odontogenic epithelium

• Odontogenic fibroma
• Myxoma [myxofibroma]
• Benign cementoblastoma (‘true’ cementoma)

Malignant Odontogenic Tumours

• Clear cell odontogenic carcinoma
• Malignant ameloblastoma
• Primary intra-osseous carcinoma
• Malignant variants of other odontogenic epithelial tumours
• Malignant changes in odontogenic cysts

Benign Odontogenic Tumours: Examples

**Ameloblastoma

Ameloblastoma - follicular pattern

L6 OdontogenicTumours, p.19

Ameloblastoma - plexiform pattern

L6 OdontogenicTumours, p.21

Unicystic ameloblastoma

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• You should remember that ameloblastoma causes bone resorption
• You should also remembmer that you HAVE to see the columanr cells with rever polarity, this is the reason we even clal it unicystic ameloblastoma Unicystic ameloblastoma Sections
• Ameloblastomas also have “baloon” or parachute cells which is another feature, although the main feature remains the columnar cells with reverse polarization

Differential diagnosis

• Dentigerous cyst
• Squamous odontogenic tumour
• Ameloblastic carcinoma

**Ameloblastic fibroma

• We have fibrous tissue which is a the main part of the tumor, we also expect to see epithelial components

  • Usually they appear in younger patients and can effect any site in the oral cavity

• You can see fibroblasts and spindle ells

  • These cells have a mixoid stroma

    • Mixoid = less collagen fibers and more ecm (i.e. Glycogen)

L6 OdontogenicTumours, p.32

**Odontoma

Compound odontome

• odontoma will remain attached to the tooth

Complex odontome

• The empty spaces will be enamel

L6 OdontogenicTumours, p.37

Compound odontome

• The prescence of ordered dental tissue is what gives the odtomoe the “compound name” it is a defining characteristic

Ameloblastic fibro odontome and ameloblastic fibrodentinoma

• You are going to see, enamel, dentine and cementum structure but with random organization
• This is essentially a mix between ameloblastic tumour and an odontome
• If it shows all layers of tooth (i.e. enamel , dentine cementum) then we call it an ameloblastic fibro odontome
• If it shows only dentine then we call it an ameloblastic fibrodentinoma
• Note that some classifications just combine this together
• 

L6 OdontogenicTumours, p.41

Odontogenic fibroma

• Usually odontogenic fibromas form a large radiolucent area which may cause root resorption

• Radiographically they appear like cysts

• The defining characteristic of an odontogenic fibroma is the epithelial islands of odontogenic epithelium, without these they would just be fibroma

  • We are not expecting to see cellular atypa(i.e. changes to morphology of the cells which causes them to be malignant (i.e. abnormal variations of nucleus and cell size)

Odontogenic myxoma

• Usually appear in the young population
• they have large spaces of myxoid tissue with less collagen fibers
• spindle shaped fibroblasts with a slightly elongated and wavy nuclues

Cementoblastoma

• Consists of cementoblasts proliferating and producing cementum

  • Sometimes they can cause resopriton of the root
  • In some caes they are well defined and they show a mixed radoiopaque and radiolucency
  • The radiograph is dependent on the amount of mineralization and calcified materials

• microscopically you can see cementoblasts with “cementum-like” material

Case Report: Journal of Oral and Maxillofacial Surgery

• Recurrent cementoblastoma associated with a developing lower second molar.
• Benign odontogenic neoplasm forming cementum-like tissue continuous with the tooth root, usually mandibular premolars or first molars.
• Presents as tender, sometimes painful swelling at buccal and lingual/palatal alveolus.
• Affects mainly individuals under 30, more common in males (1.2:1).
• Radiographically shows as a radiopaque mass with a thin radiolucent rim; shape may be rounded or irregular and mottled.
• Can cause tooth resorption, root outline loss, and obliteration of periodontal ligament space.
• Histology reveals cementum-like calcified tissue with reversal lines, sometimes[ [Pagetoid Appearance]] appearance, containing cementoblasts and cementoclasts.

Malignant odontogenic tumours (carcinomas)

Odontogenic carcinoma - pathol. fracture

• One of the side effects is that they cause bone necrosis, this can cause fracture of the jaw which can even happen without trauma
• Microscopic
  • Atypical mitosis among other malignant features
  • Because their appearance resembling odontogenic cells and the production of little calcified materials we can call them an odontogenic carcinoma

Ameloblastic carcinoma

• Frequent mitoses

• The center becomes necrotic because it doesn’t receive nutritional support!

• staining identifies the cells which are currently in mitosis

  • Those are the brown cells in this image

• Therefore the tumour can be said to have a high proliferation index

CCOC

• Keratin 19, a marker for odontogenic epithelium
• We can use the different types of cytokeratin biomarkers to identify the different types of epithelium
• Cytokeratin 19 can label odontogenic epithelia