Stafne’s Bone Defect in Atypical Location: Between the Subcondylar Region and Neck of the Mandible Ramus

CONTEXT: Stafne’s bone defect is a benign lesion appearing on the image as a round radiolucent lesion within a cortical defect on the mandible. CASE REPORT: We attend one 46-year-old male patient came for diagnostic evaluation of a rounded and radiolucent lesion in the transition of the subcondylar region and neck of the left mandible ramus incidentally found by a dentist. Computed tomography and magnetic resonance imaging were performed in medical radiology and a Stafne’s cyst was diagnosed in an atypical location. CONCLUSION: We emphasize that Stafne’s bone defect is a benign lesion, whose imaging diagnosis can be conclusive, avoiding unnecessary surgical procedures.


Introduction
Stafne bone cavity is a rare abnormality, named after Edward Stafne, who first described the lesion in 1942. The lesion is known by many synonyms, such as Stafne lacune, static bone cavity, latent bone cyst and lingual mandibular bone depression. Lingual mandibular depressions represent a group of focal defects in the lingual surface of the mandible, mimicking a cystic lesion on plain radiographs.
The pathogenesis is believed to be caused by the pressure of the submandibular glands against lingual cortical bone of the mandible. It is usually an incidental, stable and benign finding, and for this reason many authors have proposed that there is no need for treatment of these bone defects on the lingual side of the mandible. The posterior mandible region, particularly at the angle and below the mandibular canal, is the common location. However, patients may present anatomical variations, making the diagnosis challenging, often confusing with injuries of another nature and leading to unnecessary treatments. Because of this, it is interesting to know the possible anatomical variations, to make the correct diagnosis and not to cause injuries to the patient [1] [2] [3].
We will report a case of Stafne's bone cyst with an atypical presentation. Patients may have anatomical variations, making the diagnosis essential and challenging for effective management, avoiding unnecessary treatments.

Case Report
A 46-year-old asymptomatic male was admitted to the medical radiology service to investigate a lesion in the left jaw that was incidentally found in an external dental service. He performed computed tomography and magnetic resonance imaging of mandibular region. A rounded, well circumscribed and unilocular lesion was visualized at the transition between the subcondylar region and the neck of the left mandible ramus, with a fatty, soft tissue and vascular component inside. The patient was followed for one year after the initial diagnosis and there were no signs of aggressive behavior or malignancy, as verified by computed tomography and magnetic resonance imaging. Therefore, a hypothesis of a bone defect or Stafne cyst was confirmed in an atypical location in the mandible, near the deep portion of the adjacent parotid.

Discussion
In 1942, Edward Stafne reported 35 radiolucent lesions in the mandibular angle discovered on intraoral dental films. These radiolucencies are called nowadays as Stafne bone cavities. Other synonyms include: static bone cavity, latent bone cyst, bone defect of the mandible development, Stafne cyst and bone depression of the mandibular lingual cortical [4].
Recent studies support that this condition may be originated from pressure due to hyperplasia and hypertrophy of the salivary glands towards the adjacent bone surface, leading to bone remodeling in response to chronic stimuli in the cortical area. This theory could also explain the existence of anterior defects associated with the sublingual glands and defects in the ascending branches associated with the parotid glands [2] [5].
Imaging studies are indispensable for diagnosis because they provide accurate information about the soft and hard tissues in question, without the need to ex-

Conclusion
We conclude that the report of this case is important for radiologists, dentists and physicians in general, since the knowledge of atypical locations of such benign mandibular bone defects can avoid misdiagnosis or erroneous interpretation and prevent unnecessary surgical or invasive procedures.

Funding
No funding was used in this work.