Diagnostic Challenge (continued from page 60)
In 1942, Edward C. Stafne documented 34 cases of a well-defined radiolucent entity below the inferior alveolar nerve canal, near the mandibular angle.1 The entity is a developmental, lingual cortical bone concavity of the mandible that usually contains salivary gland tissue, fat, muscle, blood vessels, lymphoid tissue or fibrous connective tissue.2-4 The etiology is unknown, but the presence of salivary gland tissue in the bone concavity and its common location within the submandibular gland fossa have led some investigators to hypothesize that its development is related to the growth of the submandibular gland. Similar entities, albeit rare, in the anterior mandible and upper mandibular ramus coincide with the sites of the sublingual and parotid glands, respectively.2-5
Various names have been attributed to the cortical bone concavities, including Stafne bone defect, static bone defect, lingual mandibular salivary gland depression and lingual cortical mandibular defect. The equally synonymous terms of Stafne bone cyst, latent bone cyst and static bone cyst only serve to describe the radiographic cyst-like appearance of the entity; they do not describe the true nature of the entity because the entity has no epithelial lining and is, therefore, not a true cyst.
The typical scenario of a Stafne bone defect is an incidental finding below the inferior alveolar nerve canal near the angle of the mandible on a panoramic radiograph. An incidence of 0.3% has been reported for Stafne bone defects of the posterior mandible on panoramic radiographs.2,3 Most cases are unilateral and occur in 50-60 year old males.2,3,5 The bone concavity is asymptomatic and very difficult, if not impossible, to palpate clinically even if the inferior aspect of the defect coincides with the inferior border of the mandible. The Stafne bone defect is projected on radiographs as a round or oval, completely radiolucent entity with a well-defined, sclerotic periphery (Fig.1).
Given the typical radiographic features and location, which is away from the teeth and sources of odontogenic lesions, a confident presumptive diagnosis can be made without further investigation. However, when a defect presents in an unusual location or with non-classic features, further investigation is required to rule out other pathologic processes. In the case presented in this challenge the radiolucency extends superior to the inferior alveolar nerve canal and is closely related to the tooth. Therefore, a CT was performed which demonstrates the well-defined, smooth, lingual cortical concavity (Fig.2a and b), confirming the diagnosis of a Stafne bone defect. Biopsy and treatment are not required for patients with Stafne bone defects. Although they may be seen to enlarge over time, the prognosis is excellent.
References
1. Stafne EC. Bone cavities situated near the angle of the mandible. J Am Dent Assoc 1942;29:1969-72.
2. Neville BW, Damm DD, Allen CA, Bouquot JE. Oral and maxillofacial pathology (ed 3). St. Louis, United States of America, Saunders, Elsevier, 2009.
3. Sciubba JJ, Fantasia JE, Kahn LB. Atlas of tumor pathology: Tumors and cysts of the jaws, third series, fascicle 29. Washington, D. C., United States of America, Armed Forces Institute of Pathology, 2001.
4. White SC, Pharoah MJ. Oral radiology: Principles and interpretation (ed 6). St. Louis, United States of America, Mosby, Inc., 2009.
5. Philipsen HP, Takata T, Reichart PA, Sato S, Suei Y. Lingual and buccal mandibular bone depressions: a review based on 583 cases from a world-wide literature survey, including 69 new cases from Japan. Dentomaxillofac Radiol. 2002;31:281-90.
Acknowledgment
The authors would like to thank Dr. Ernie Lam for contributing the case for this challenge. OH
Dr. Chan completed the Doctor of Dental Medicine program at the University of British Columbia in 2006, and the 3-year Oral and Maxillofacial Pathology residency at Long Island Jewish Medical Center in New York in 2009. She is a Fellow in the Royal College of Dentists in Canada in Oral Pathology, and board certified by the American Board of Oral and Maxillofacial Pathology. She is currently a resident in Oral Radiology at the Faculty of Dentistry, University of Toronto.
Dr. Susanne Perschbacher, DDS, MSC, DIP. ABOMR, FRCD(C) Oral and Maxillofacial Radiology. Dr. Perschbacher is a member of the editorial board for Oral Health Journal.
