The differential diagnosis of osseous jaw lesions includes numerous entities. A specific mandibular bone defect known as Stafne's cavity or cyst presents wirh a characteristic cyst-like lesion on radiographs of the jaw. Although the differential diagnosis from other jaw lesions is mandatory, this lesion does not usually require surgical therapy. Current theories concerning the pathogenesis of Stafne's cavity prefer bone depression as a consequence of constant pressure arising from an adjacent salivary gland. We present a case of a large Stafne's cavity eroding the basal mandibular cortex that was found accidentally on an orthopantogram taken for diagnosis of dental diseases. The patient noted a slight pain on pressure during physical investigation. The lesion was completely occupied by fatty tissue, as shown during surgical exploration and as revealed by histological investigation of the specimen. The theory of parenchymal pressure as the cause of mandibular bone depression appears to be inapplicable in the present case. The pathogenesis of Stafne's cavity is still obscure. Differential diagnosis of mandibular lesions is essential in adequate treatment planning.
