Odontogenic cysts and tumours
- Lesion
Cysts and tumours of the jaws arise from tooth-forming tissues. Most are benign, but some, like the keratocyst and ameloblastoma, are locally aggressive.
What it is
Unlike other bones, the jaws often contain epithelium-lined cysts, because remnants of odontogenic epithelium persist there. Cysts are inflammatory (periapical) or developmental (dentigerous, odontogenic keratocyst), and are classified by their relation to a tooth. Odontogenic tumours come from odontogenic epithelium, mesenchyme or both; the odontoma and ameloblastoma are the most important.
Structure
- Periapical cyst: lining of non-keratinised squamous epithelium with chronic inflammation, cholesterol clefts and foam cells.
- Dentigerous cyst: thin stratified squamous lining attached to the crown's neck.
- Keratocyst: thin, corrugated parakeratinised lining with a prominent palisaded basal layer; satellite cysts in the wall.
- Ameloblastoma: islands of epithelium with peripheral palisaded columnar cells with reversed polarity around loose stellate reticulum-like cells.
Step by step
- Remnants of tooth-forming epithelium (rests of Malassez, reduced enamel epithelium, dental lamina) remain in the jaw.
- Inflammation from a dead pulp stimulates the rests at the apex to proliferate and form a cyst.
- Fluid collecting between the crown and the follicle of an unerupted tooth makes a dentigerous cyst.
- Mutations in the Hedgehog pathway (PTCH1) drive keratocysts; BRAF V600E is common in ameloblastoma.
- The lesions expand the bone by pressure and resorption.
Jaw cysts and tumours
| Lesion | Relation to tooth | Key histology | Behaviour |
|---|---|---|---|
| Periapical cyst | Apex of a non-vital tooth | Inflamed squamous lining | Benign, resolves with treatment |
| Dentigerous cyst | Crown of an unerupted tooth | Thin squamous lining | Benign |
| Odontogenic keratocyst | Any | Parakeratin, palisaded basal layer | Locally aggressive, recurs |
| Odontoma | Often with unerupted tooth | Enamel and dentin | Hamartoma |
| Ameloblastoma | Posterior mandible | Palisaded cells with reverse polarity | Locally invasive |
Clinical notes
- Most are found on dental radiographs or as painless jaw swelling.
- Keratocysts need complete removal because recurrence is frequent.
- Gorlin syndrome: multiple keratocysts, basal cell carcinomas, palmar pits, calcified falx.
Test yourself
Think of the answer, then tap the question to see it.
Where does a dentigerous cyst form?
Around the crown of an unerupted tooth, most often an impacted third molar.
Which syndrome should multiple odontogenic keratocysts suggest?
Nevoid basal cell carcinoma (Gorlin) syndrome, caused by germline PTCH1 mutations.
What is the most common odontogenic tumour?
The odontoma, a hamartoma of enamel and dentin.
Elsewhere in DurgiPedia
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Mouth Disorders (MedlinePlus, US National Library of Medicine, 2025).
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Representative model, for educational purposes only.