Atypical Stafne Bone Cavity

Abstract

A patient was referred to the Department of Oral and Maxillofacial Surgery for extraction of the lower-left third molar tooth. There had been one episode of pericoronitis 5 years previously, since which there had been no symptoms. A panoramic radiograph showed a partially erupted mesioangularly impacted third molar without associated disease. Clinically no inflammation was present, and in the absence of specific indications for its removal, the tooth was left in situ. However, the radiograph revealed a radiolucency in the contralateral side of the mandible, below the fully-erupted lower-right third molar. The radiolucency measured approximately 2.5 cm £ 2.0 cm and was rhomboidal in shape. It extended from the apices of the lower-right second and third molars to the lower border of the mandible and was well defined with a corticated smooth but irregular margin (Fig. 1). The roots of the teeth were not resorbed and the periodontal ligament space and lamina dura appeared normal. The lesion was asymptomatic, and all teeth in the lower-right quadrant proved vital on electric pulp testing. Further radiographic views, a lower 908 occlusal and postero-anterior jaws were taken but did not add any further information. The most likely diagnosis was a Stafne bone cavity, but because of the unusual shape and extent, axial computed tomography (CT) (volume scan, 3 mm slices) was performed, and this showed a well-defined lingual defect in the posterior aspect of the right side of the mandible (Fig. 2). The buccal cortex was thinned and expanded and possibly perforated, though this last feature could not be differentiated from partial volume artefact. The cavity was partially filled by soft tissue that appeared to be continuous with the submandibular gland, but contained areas of a lower density, similar to the density of parotid gland. However a benign soft tissue tumour could not be excluded Based on these investigations the patient was informed of the likely diagnosis of Stafne bone cavity, and review to observe the lesion and thus confirm the diagnosis was recommended. However, aware of the unusual features, the patient was keen to obtain a definitive diagnosis and requested biopsy despite the proximity of the inferior alveolar nerve and the risk of nerve injury. Under general anaesthesia an intraoral buccal mucoperiosteal flap was raised and buccal bone removed with a bur. The cavity was found to be filled with salivary gland tissue and an incisional biopsy performed. Histopathological examination revealed an un-inflamed salivary gland with a normal duct and lobular structure and mild adipose replacement. At higher power the gland was found to be composed almost exclusively of serous acini with occasional clusters of mucous acini, consistent with the distal pole of the submandibular gland. A final diagnosis of Stafne idiopathic salivary gland inclusion was made (Fig. 3). Two months postoperatively the patient had some residual but resolving paraesthesia of the right mental nerve and did not return for further followup.