Clinical Radiology Extra (2003) 58: 51–53 doi:10.1016/S1477-6804(03)00011-6, available online at www.sciencedirect.com

Case Report

Atypical Stafne Bone Cavity

N. A. DRAGE, T. RENTON, E. W. ODELL

Guy’s King’s and St Thomas’ Dental Institute, Guy’s Hospital and King’s College, London, UK

INTRODUCTION despite the proximity of the inferior alveolar nerve and the risk of nerve injury. Under general anaesthesia an intraoral buccal mucoperiosteal flap was This report describes an unusual Stafne bone cavity (lingual raised and buccal bone removed with a bur. The cavity was found to be mandibular salivary inclusion or ) with an irregular shape, filled with salivary gland tissue and an incisional biopsy performed. extension above the inferior dental canal and expansion of the Histopathological examination revealed an un-inflamed salivary gland with buccal cortex. These features are beyond the range normally a normal duct and lobular structure and mild adipose replacement. At higher power the gland was found to be composed almost exclusively of accepted for this entity and rendered differential diagnosis serous acini with occasional clusters of mucous acini, consistent with the difficult, prompting biopsy to confirm the diagnosis. distal pole of the . A final diagnosis of Stafne idiopathic salivary gland inclusion was made (Fig. 3). Two months postoperatively the patient had some residual but resolving CASE REPORT paraesthesia of the right mental nerve and did not return for further follow- up. A patient was referred to the Department of Oral and Maxillofacial for extraction of the lower-left third molar . There had been one episode of 5 years previously, since which there had been DISCUSSION no symptoms. A showed a partially erupted mesio- angularly impacted third molar without associated disease. Clinically no inflammation was present, and in the absence of specific indications for its Mandibular salivary gland inclusions were first reported by removal, the tooth was left in situ. Stafne (1942) as incidental findings on dental radiographs [1]. However, the radiograph revealed a radiolucency in the contralateral He defined the classical appearances that allow definitive side of the , below the fully-erupted lower-right third molar. The diagnosis on radiological grounds alone, and showed that the radiolucency measured approximately 2.5 cm £ 2.0 cm and was rhomboi- dal in shape. It extended from the apices of the lower-right second and third contained salivary tissue. molars to the lower border of the mandible and was well defined with a Since then the has been described many times under corticated smooth but irregular margin (Fig. 1). The roots of the teeth were different names but its aetiology remains a mystery. It is not resorbed and the periodontal ligament space and lamina dura appeared unlikely to be a developmental anomaly because it is almost normal. The lesion was asymptomatic, and all teeth in the lower-right quadrant proved vital on electric pulp testing. Further radiographic views, a never found in children and is commonest in the middle aged lower 908 occlusal and postero-anterior were taken but did not add any and elderly. Possible causes are speculative [2], and most further information. authors accept, though without good evidence, that the lesions The most likely diagnosis was a Stafne bone cavity, but because of the may arise by pressure atrophy caused by the submandibular unusual shape and extent, axial computed tomography (CT) (volume scan, gland. Lesions do not appear to enlarge with age. 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 Differential diagnosis is not usually problematic. As cortex was thinned and expanded and possibly perforated, though this last originally described by Stafne, the typical features of a well- feature could not be differentiated from partial volume artefact. The cavity circumscribed, corticated, oval or round radiolucency between was partially filled by soft tissue that appeared to be continuous with the the inferior dental canal and lower border of the mandible at 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 angle are sufficient for definitive diagnosis on radiological excluded grounds alone. It is rarely bilateral. Based on these investigations the patient was informed of the likely However, the lesion can cause problems when its appear- diagnosis of Stafne bone cavity, and review to observe the lesion and thus ances differ from the typical [3]. The present case exemplifies confirm the diagnosis was recommended. However, aware of the unusual features, the patient was keen to obtain a definitive diagnosis and requested these problems, showing a combination of three unusual features: irregular shape, abnormal extent and expansion of the Guarantor and correspondent: Nicholas A. Drage, Department of Dental mandibular cortex. Radiology, University Dental Hospital, Heath Park, Cardiff CF14 4XY, Lesions are usually round or ovoid with only convex edges UK; E-mail: [email protected] radiographically. The shape of this lesion was rhomboidal with 1477-6804/03/$30.00/0 q 2003 The Royal College of Radiologists. Published by Elsevier Science Ltd. All rights reserved. 52 CLINICAL RADIOLOGY

Fig. 1 – Cropped panoramic radiograph showing well-defined corticated rhomboidal radiolucency in the right mandible. There was no effect on the root apices of the adjacent teeth. The inferior dental canal is arrowed. partially straight or concave edges. Salivary lesions are characteristically located below the inferior dental canal between the angle and the first molar tooth. Anteriorly placed inclusions are the commonest variation in site and are well- recognized, but much less frequent than posterior lesions [4]. The present case, while at the typical site, extended a significant distance above the inferior alveolar canal to the apices of the molar teeth. This is a rare finding and has only been reported in a few lesions [5,6]. The rarest feature of the present case is the expansion, which has been reported occasionally [7], and appears to indicate a true submandibular salivary gland inclusion rather than a fatty tissue inclusion [8]. Other lesions that can present as a unilocular radiolucency include radicular cyst, , traumatic , central giant cell granuloma and ameloblastoma. The radicular cyst is associated with the apex of a non-vital tooth. The adjacent teeth proved to be vital and the lamina dura was intact around the root apices and so could be excluded from the differential diagnosis. The odontogenic keratocyst is commonly seen in the posterior mandible and is often associated with an impacted tooth [9]. They can grow very large before they are detected because they tend to cause only slight expansion of the . The can have similar radiographic features to that of an odontogenic keratocyst and also has a tendency to arch up in between the roots of the teeth [10]. The central giant cell granuloma is more commonly found anterior to the lower first molar and often causes marked expansion of the bone, displacement of teeth and resorption of the lamina dura [11,12], features not seen in this case. The ameloblastoma is often an expansile lesion [9] that causes resorption and displacement of the adjacent teeth. These latter features again were not seen in this case. Reports of osteomyelitis [13] and non-odontogenic tumours Fig. 2 – CT (a, soft tissue windows; b, bony windows) showing soft tissue mass (arrowed) on the lingual cortex of the mandible showing bony buccal [14] mimicking salivary inclusions with atypical appearances expansion. The mass appears continuous with the right submandibular on radiology mean that they merit further investigation. In the gland. Areas of low attenuation are present within the mass. present case CT showed a heterogeneous soft tissue density within a well-defined bony defect. This raised concern that the salivary tissue within the defect might possibly be a benign slow-growing salivary gland lesion. However, the density was similar to the parotid gland, and after biopsy, proved consistent CASE REPORT 53

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