Adenomatoid Odontogenic Tumour

Adenomatoid odontogenic tumour is a benign, slow growing, encapsulated odontogenic tumour of epithelial origin. It makes up about 3 to 7% of odontogenic tumours.

It occurs mainly in the second decade, with a female predominance of about 2 to 1, and in the anterior maxilla, particularly the canine region. Most are the follicular type attached to an unerupted tooth, with extrafollicular and peripheral types being less common.

Pathophysiology. The tumour is composed of odontogenic epithelium in whorled sheets and duct like structures, with eosinophilic material and calcification. Activating KRAS mutations have been found in a large proportion of cases.

It is a hamartoma like lesion with limited growth potential and a thick fibrous capsule, which accounts for its non-recurring behaviour.

Painless swelling of the jaw, often found because a tooth, usually the canine, fails to erupt. The cortex may be expanded and the neighbouring teeth displaced. Peripheral lesions are firm, pink gingival swellings.

Pain, rapid growth and mobility are not typical.

• Panoramic and periapical radiographs: a well defined unilocular radiolucency around the crown of an unerupted tooth (like a dentigerous cyst), often extending along the root, with fine radiopaque calcifications (snowflake pattern).
• Cone beam CT: size, relation to adjacent teeth and nasal floor, and calcification.
• Histology of the enucleated specimen: spindle cells in whorls and rosettes, duct like spaces lined by columnar cells, eosinophilic material and calcification, in a thick capsule.
• Biopsy before surgery when the clinical picture is atypical.

Differential diagnosis.

• Dentigerous cyst
• Calcifying odontogenic cyst
• Calcifying epithelial odontogenic tumour
• Unicystic ameloblastoma
• Ameloblastic fibro odontoma and odontoma
• Odontogenic keratocyst
• Lateral radicular cyst

• Enucleation with curettage, taking out the tumour with its capsule. This is curative, and recurrence is very rare, under 0.2% in published series.
• Preserve the associated unerupted tooth when possible, with surgical exposure and orthodontic traction after the tumour is removed. Extract the tooth when it is displaced, damaged or in the line of surgery.
• Antibiotics only for infection with spread: amoxicillin 500 mg orally three times daily for 5 days (reduce to 500 mg every 12 hours at eGFR 10 to 30), or clindamycin 300 mg four times daily in penicillin allergy.
• Analgesia: paracetamol 1 g every 6 hours (maximum 4 g daily) with ibuprofen 400 mg every 8 hours with food.

Special groups. Children need weight based dosing and paediatric anaesthesia for larger operations, with coordinated orthodontic care for the impacted tooth.

Monitoring. Radiographs at 6 and 12 months for bone fill and the position of the preserved tooth, and a final review at 2 years. Long term surveillance is not usually needed.

Referral and escalation. Refer to oral and maxillofacial surgery for removal and to an orthodontist when the tooth is kept. Urgent referral for an unusual aggressive course.