Squamous Odontogenic Tumour

Squamous odontogenic tumour is a rare benign odontogenic tumour of squamous epithelial islands in a fibrous stroma. It arises in the periodontal ligament region lateral to a root or at the root apex, and mostly in young to middle aged adults.

It occurs in the maxilla and mandible with a slight preference for the maxillary incisor to premolar region and the mandibular molar area. Fewer than 100 cases were reported in older series, so published information is limited.

Pathophysiology. Derived from the epithelial rests of Malassez, the tumour forms islands of bland squamous cells with peripheral flattening and no ameloblastic features, with microcystic change and focal keratinisation or calcification.

Multiple or familial lesions have been reported, with involvement of several quadrants. Behaviour is slow growing and non-invasive in most.

Mild swelling, tooth mobility, tenderness on biting or gingival swelling, or an incidental radiographic finding. Pain is unusual. Mobility of neighbouring teeth with bone loss can resemble periodontal disease, and many are found at dental review for this reason.

Rapid growth, mobile teeth in several areas or destruction suggests another diagnosis.

• Periapical or panoramic radiograph: a triangular or semicircular radiolucency at the lateral root surface between teeth, with a well defined border, suggesting an intrabony defect. Larger lesions can be multilocular.
• Pulp sensibility tests: the involved teeth are usually vital.
• Cone beam CT for extent and relation to vital structures.
• Biopsy and histology: islands of squamous epithelium, with microcysts, calcification and keratinisation, and a fibrous stroma. Distinguish from squamous cell carcinoma and ameloblastoma.
• Periodontal probing for deep isolated defects.

Differential diagnosis.

• Periodontitis with intrabony defect
• Lateral periodontal cyst
• Ameloblastoma
• Intraosseous squamous cell carcinoma
• Lateral radicular cyst
• Langerhans cell histiocytosis
• Central giant cell granuloma

• Conservative surgical excision with curettage, preserving involved teeth when possible, and extraction when teeth are mobile with loss of support. This is usually curative.
• Recurrence is about 15 to 20% in reports with limited numbers, and is managed by re-excision. Larger or recurrent tumours need local resection with a margin.
• 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.
• Periodontal care after surgery, with splinting of mobile teeth where needed.

Monitoring. Review at 3, 6 and 12 months, then annually for at least 5 years, with radiographs and periodontal charting.

Referral and escalation. Refer to oral and maxillofacial surgery for biopsy and planning. Urgent referral for rapid growth, multifocal lesions or histology suggesting carcinoma.