Stafne Bone Defect

Stafne bone defect is a developmental lingual concavity in the mandible that contains salivary gland tissue, most often a lobe of the submandibular gland, and shows on a radiograph as a well defined radiolucency. It is not a true cyst and is not a disease.

It is found on up to 0.5% of panoramic radiographs, mostly in men in the fifth to seventh decades. The classic site is the posterior mandible, between the molars and the angle, inferior to the mandibular canal.

Pathophysiology. Pressure and local remodelling from an aberrant lobe of salivary gland, or from vascular and other tissue, create a depression on the lingual surface of the bone.

An anterior variant, with sublingual gland tissue, is rare. The defect is stable or grows very slowly, and a cause such as a cyst or tumour is not present.

No symptoms and no swelling, found by chance. The overlying mucosa and teeth are normal. A bony concavity may be palpable on the lingual surface of the mandible in the molar region.

Pain, swelling, sensory change or a rapidly growing lesion is not a feature, and these point to a different diagnosis.

• Panoramic radiograph: a round or oval, well defined radiolucency, 1 to 3 cm, with a thin corticated border, in the posterior mandible inferior to the inferior alveolar canal, near the angle.
• Cone beam CT: a concave defect on the lingual cortex, with soft tissue content continuous with the submandibular gland. This confirms the diagnosis and avoids biopsy.
• MRI or ultrasound to show salivary gland tissue within the defect, and sialography when needed.
• Biopsy only for atypical features: unusual position, expansion, a lesion on the buccal cortex, growth on follow up, or lack of confirmation on CT.

Differential diagnosis.

• Odontogenic keratocyst and other jaw cysts
• Residual cyst
• Ameloblastoma
• Simple bone cyst
• Central giant cell granuloma
• Metastasis and brown tumour of hyperparathyroidism
• Osteomyelitis and mandibular canal variants
• Lingual salivary gland tumour or neurogenic tumour

• No treatment. Counsel the patient and record the finding clearly in the notes to avoid unnecessary surgery.
• Confirm the diagnosis with cone beam CT, MRI or ultrasound when the appearance is classic. If imaging is typical, no biopsy is needed.
• Atypical features, or a position away from the usual site: biopsy and referral to oral and maxillofacial surgery.
• Surgery is not indicated even if the defect grows slowly, unless there is a diagnostic question. Surgical exploration carries a risk of damage to the lingual nerve and the submandibular gland.

Monitoring. Repeat panoramic radiograph at 6 to 12 months to confirm stability, and then only for new symptoms. Growth or change in appearance needs re-imaging and biopsy.

Referral and escalation. Refer to oral and maxillofacial surgery or oral medicine when the radiograph is atypical, imaging is not confirmatory or the lesion changes. Routine dental follow up is otherwise enough.