Odontogenic Tumors
Adenomatoid Odontogenic Tumour
aka AOT · Adenoameloblastoma (obsolete) · Two-Thirds Tumour
Benign encapsulated odontogenic epithelial tumour with duct-like structures; classically presents as a pericoronal lesion around an unerupted maxillary canine in a young female — the 'two-thirds tumour'.
Red Flags
- ·Rapid growth would prompt biopsy to exclude ameloblastoma or malignancy
Clinical Tips
- ·An AOT can be safely enucleated — its thick fibrous capsule shells out cleanly, unlike an ameloblastoma.
Examination Checklist
- ·Check for missing permanent canine
- ·OPG + IOPA
- ·CBCT
- ·Vitality of adjacent teeth
§ figuresFigures (3)
Fig. 1The adenomatoid odontogenic tumor is an odontogenic tumor arising from the enamel organ or dental lamina.
“Adenomatoid odontogenic tumor” · JXtra · CC BY-SA 3.0 · Wikimedia Commons
Verified open-access images only, reproduced for education under their stated licences · no AI-generated or illustrative artwork · Adenomatoid Odontogenic Tumour figures pending faculty review.
§ overviewOverview
A benign, slow-growing, well-encapsulated odontogenic tumour derived from odontogenic epithelium, characterised by duct-like structures and variable calcifications.
§ icdICD Classification
ICD-10 D16.4/D16.5
§ etiologyEtiology
- 01Origin from reduced enamel epithelium or dental lamina remnants
§ riskRisk Factors
- 01Nil identified
§ geneticsGenetics & Molecular Biology
- 01No specific mutation; sporadic
§ epidemiologyEpidemiology
3–7% of odontogenic tumours. 'Two-thirds tumour': 2/3 in females, 2/3 in maxilla, 2/3 in 2nd decade, 2/3 associated with unerupted tooth, 2/3 involve the canine.
§ pathogenesisPathogenesis
Proliferation of odontogenic epithelium with formation of duct-like structures and calcifications; encapsulation limits its aggressiveness.
§ clinicalClinical Features
- 01Painless, slow-growing swelling in the anterior jaw
- 02Unerupted tooth (usually maxillary canine)
- 03Cortical expansion when large
§ signsSigns & Symptoms
- 01Missing permanent tooth in the arch
- 02Occasional egg-shell crackling
§ differentialDifferential Diagnosis
- 01Dentigerous cyst
- 02OKC
- 03Calcifying odontogenic cyst
- 04Ameloblastoma (unicystic)
- 05CEOT
§ criteriaDiagnostic Criteria
- 01Pericoronal radiolucency extending apically beyond CEJ
- 02Fine flecks / 'snowflake' calcifications
- 03Encapsulated on histology with duct-like (rosette) structures
§ histopathHistopathology
- 01Thick fibrous capsule
- 02Whorled masses / rosettes of spindle to cuboidal odontogenic epithelial cells
- 03Duct-like structures lined by columnar cells
- 04Foci of calcification (dystrophic, tubular dentin, or cementum-like)
- 05No stellate reticulum, no palisading of basal cells (differentiates from ameloblastoma)
§ radiographicRadiographic Features
- 01Unilocular radiolucency around crown extending apically beyond CEJ (key differentiator from dentigerous)
- 02Fine 'snowflake' radiopaque flecks within
- 03Well-defined corticated margin
§ opgOPG Findings
- 01Screening; identify associated unerupted canine
§ cbctCBCT Findings
- 013D relation to sinus/nasal cavity, adjacent roots and neurovascular structures
§ ctCT Findings
- 01Rarely required
§ mriMRI Findings
- 01Not indicated
§ investigationsInvestigations
- 01Clinical + radiographic + histopathological correlation
- 02CBCT for surgical planning
§ labsLaboratory Findings
- 01Non-specific
§ ihcIHC / Special Stains
- 01CK-14, CK-19 positive; amelogenin often positive; Ki-67 low (< 5%)
§ whoWHO Classification
WHO 2022: Benign odontogenic tumour of epithelial origin — Adenomatoid odontogenic tumour.
§ classificationClassification
- 01Follicular (pericoronal, 73%) — most common
- 02Extrafollicular (24%) — between roots, no associated unerupted tooth
- 03Peripheral (3%) — extraosseous, gingival
§ planTreatment Planning
- 01Enucleation is curative
- 02Preserve adjacent teeth when possible
- 03Orthodontic traction of impacted canine after removal
§ treatmentTreatment
- 01Conservative surgical enucleation with removal of capsule
- 02Extract or orthodontically align associated impacted tooth
§ medicalMedical Management
- 01Nil
§ surgicalSurgical Management
- 01Enucleation with careful capsule removal
§ reconstructionReconstruction Options
- 01Small defects heal spontaneously; occasional bone graft
§ complicationsComplications
- 01Loss of associated tooth
- 02Recurrence extremely rare
§ recurrenceRecurrence Rate
< 1% — essentially cured by enucleation.
§ followupFollow-up Protocol
- 016- and 12-month post-op OPG
§ prognosisPrognosis
Excellent.
§ preventionPrevention
- 01None applicable
§ examKey Examination Points
- 01Young female + maxillary canine + pericoronal radiolucency with flecks = AOT
- 02Extends apical to CEJ — critical differentiator from dentigerous cyst
§ revisionQuick Revision Summary
- 01Two-thirds tumour
- 02Encapsulated
- 03Duct-like rosettes with dystrophic calcification
- 04Enucleation is curative
§ vivaBDS Viva Questions
- 01Why is AOT called the 'two-thirds tumour'?
- 02How do you differentiate AOT from a dentigerous cyst radiographically?
- 03Histological features of AOT.
- 04Treatment of AOT.
- 05Recurrence rate.
- 06Variants of AOT.
- 07Origin of AOT.
- 08Differential diagnosis of pericoronal radiolucency.
- 09IHC of AOT.
- 10Age and sex predilection.
§ bdsBDS Professional Examination
- 01Short note: Adenomatoid odontogenic tumour.
- 02Short essay: Two-thirds tumour.
§ fcpsFCPS Residency Questions
- 01Discuss the differential diagnosis of a pericoronal radiolucency associated with an impacted maxillary canine.
§ pearlsClinical Pearls
- 01Adenomatoid ≠ adenocarcinoma — this is a benign encapsulated lesion.
- 02Snowflake calcifications extending apically past the CEJ = AOT, not a dentigerous cyst.
§ mnemonicsMnemonics
- 01AOT = All 2/3 — female, maxilla, canine, teens, follicular, encapsulated
§ readingSuggested Reading
- 01Philipsen HP, Reichart PA. Adenomatoid odontogenic tumour: facts and figures. Oral Oncol 1999.
§ differentialDifferential Comparison
| Entity | Feature | Distinguisher |
|---|---|---|
| Dentigerous cyst | Radiolucency at CEJ | AOT extends apically beyond CEJ, shows flecks of calcification |
| CEOT | Driven snow | Middle-aged, posterior mandible, Liesegang rings |
| COC | Ghost cells + calcifications | Histology diagnostic |
§ mcqsMCQs — Assessment (20)
Question 1
AOT is known as:
Question 2
Most common site of AOT:
Question 3
Key differentiator from dentigerous cyst:
Question 4
Histologic hallmark of AOT:
Question 5
Treatment of choice:
Question 6
Recurrence rate:
Question 7
Age group most affected:
Question 8
Sex predilection:
Question 9
Most common variant of AOT:
Question 10
AOT origin is from:
Question 11
Which is TRUE?
Question 12
Radiographic feature that suggests AOT over dentigerous cyst:
Question 13
Ki-67 index in AOT is:
Question 14
Ameloblast-like palisading is:
Question 15
Peripheral AOT presents as:
Question 16
Follicular AOT is associated with:
Question 17
Which is the least common variant?
Question 18
AOT is more common in:
Question 19
Which tooth is most often associated?
Question 20
Best imaging modality for AOT is:
§ evidenceReferences & Evidence
Current Classification
WHO Classification of Head and Neck Tumours
5th Edition — Volume 9
WHO Classification of Tumours Editorial Board · 2022
The authoritative international classification of head and neck, odontogenic and salivary gland tumours. Current terminology on this site follows this edition.
Evidence summary
Highest level of evidence linked to this page: WHO / Official Classification.
- L1 · Classification — 3
- L4 · Research — 1
- L6 · Textbook — 3
1 linked source was published from 2024 onwards. Where guidance is limited or contested, rely on the higher-level sources above rather than this summary. Educational use only — not a substitute for clinical judgement.
Content last reviewed
September 2026
Evidence last reviewed
September 2026
Next scheduled review
September 2027
Review status
EVIDENCE REVIEWED
Search latest PubMed evidence
Last literature search: 7 September 2026
Current Classification
WHO Classification of Tumours Editorial Board. IARC / World Health Organization · 2022
The authoritative international classification of head and neck, odontogenic and salivary gland tumours. Current terminology on this site follows this edition.
Vered M, Wright JM. Head and neck pathology · 2022 · 16(1):63-75
Summary of odontogenic and maxillofacial bone tumour changes in the 5th edition WHO classification.
IARC / WHO. IARC · 2022
Continuously updated online edition of the WHO head and neck tumour classification.
Radiology References
Dunfee BL, Sakai O, Pistey R et al.. Radiographics : a review publication of the Radiological Society of North America, Inc · 2006 · 26(6):1751-68
Radiologic-pathologic correlation of benign and malignant odontogenic lesions of the jaws.
Histopathology References
Barnes L. CRC Press · 2008
Detailed histopathological reference for head and neck diagnostic criteria.
Textbook References
Neville BW, Damm DD, Allen CM et al.. Elsevier · 2024
Standard reference textbook of oral and maxillofacial pathology used throughout this atlas.
Rajendran R, Sivapathasundharam B. Elsevier · 2020
Undergraduate and postgraduate oral pathology textbook widely used in BDS and FCPS curricula.
Additional sources cited on this page
- WHO Classification of Head and Neck Tumours, 5e (2022)
- Neville BW. Oral and Maxillofacial Pathology, 4e
- Shafer's Textbook of Oral Pathology, 9e
Draft — pending faculty review. Educational use only; verify against current guidelines and primary sources before clinical application.