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# 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.

Updated Nov 12, 2026

## Key points

- Periapical (radicular) cyst: commonest, at the root apex of a non-vital tooth after pulpitis and necrosis; 'periapical granuloma' is not a true granuloma.
- Dentigerous cyst: around the crown of an unerupted tooth, often an impacted third molar; unilocular.
- Odontogenic keratocyst: aggressive, recurs often; thin keratinised lining with a palisaded basal layer; multiple keratocysts suggest Gorlin syndrome (PTCH1).
- Odontoma: commonest odontogenic tumour, a hamartoma of enamel and dentin; cured by excision.
- Ameloblastoma: from odontogenic epithelium; cystic, slow, locally invasive; 'soap bubble' multilocular radiolucency in the posterior mandible; needs wide resection.

## 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.

## Memory aid

Apex = periapical, crown = dentigerous, keratin = keratocyst that keeps coming back.

## 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.

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## Elsewhere in DurgiPedia

- [Teeth](https://durgical.com/en/embryology/teeth/)

## Connections

## Related 3

- [Benign vs malignant tumours: the comparison table](https://durgical.com/en/general-pathology/benign-vs-malignant-tumours-the-comparison-table/)
- [Caries, gingivitis and periodontitis: the lesion view](https://durgical.com/en/general-pathology/caries-gingivitis-and-periodontitis-the-lesion-view/)
- [Neck cysts and paraganglioma](https://durgical.com/en/general-pathology/neck-cysts-and-paraganglioma/)

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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](https://medlineplus.gov/mouthdisorders.html) (MedlinePlus, US National Library of Medicine, 2025).

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/odontogenic-cysts-and-tumours/