Stafne bone cavity

Stafne cysts, also known as a static bone cavity of the mandible or lingual salivary gland inclusion defect, are cortical defects near the angle of the mandible below the mandibular canal. Strictly speaking, it is not a cyst since it does not contain any fluid. It is usually an incidental finding and represents a depression in the medial aspect of the mandible filled by part of the submandibular gland or adjacent fat. 

Epidemiology

Stafne cysts are most frequently seen in middle-aged men. The estimated prevalence ranges around 0.10-0.48% ².

Pathology

Stafne cysts are thought to result from remodelling of the bone by adjacent salivary tissue and have been noted to regress following resection of the gland nearby. 

Location

They generally appear in the area between the mandibular first molar and the mandibular angle ⁶.

Radiographic features

Plain radiograph and CT

Stafne's defect is usually discovered by chance during routine dental radiography. Radiographically, it is a well-circumscribed, monolocular, round, radiolucent defect, 1-3 cm in size, usually between the inferior alveolar nerve and the inferior border of the posterior mandible between the molars and the angle of the jaw. The radiolucent defect may be superimposed on the lower anterior teeth and be mistaken for an odontogenic lesion. Sometimes the defect may interrupt the contour of the lower border of the mandible, and may be palpable.

CT will show a shallow defect through the medial cortex of the mandible with a corticated rim and no soft tissue abnormalities, with the exception of a portion of the submandibular gland herniating into the defect.

The Stafne defect also tends to not increase in size or change in radiographic appearance over time (hence the term "static bone cyst"), and this can be used to help confirm the diagnosis.

Sialography may be sometimes used to help demonstrate the salivary gland tissue within the bone.

MRI

MRI can delineate the continuation of submandibular gland into the mandibular defect as an alternative to CT.

Differential diagnosis

Its main claim to fame is that it should not be confused with other lytic lesions of the jaw.

History and etymology

They are named after Edward C Stafne an American dentist (1894-1981).