Aneurysmal Bone Cyst of the Mandible Associated with an Impacted Tooth; a Case Report

Introduction: Aneurysmal bone cyst is a non-neoplastic lesion affecting mainly the long bones and spine. Only 1.8% of aneurysmal bone cysts involve the head and neck area with mandible being more commonly affected. A wide range of pathologies are included in differential diagnoses of ABC. Case Presentation: We report a case of mandibular aneurysmal bone cyst in a 15-year-old female that could be mistaken with a dentigerous cyst due to its association with an impacted tooth, although unlike dentigerous cyst it was accompanied by pain and swelling. Radiographically, an unilocular ill-defined radiolucency surrounding the third molar tooth germ was detected. performing fine needle aspiration, a low viscosity bloody fluid was aspirated. Incisional biopsy followed by microscopic evaluation revealed blood-filled spaces surrounded by hypercellular inflamed fibrotic connective tissue, suggesting an ABC. Due to the risk of association with true neoplastic lesions, the whole lesion was excised via extraoral approach and histopathologic evaluation confirmed the diagnosis of ABC. 7 years of follow-up showed no complications or signs of recurrence. Conclusion: Association with unerupted or impacted tooth is not a common finding for aneurysmal bone cysts. It means that it can mimic radiographical features of dentigerous or other odontogenic cysts. Although aspiration may be helpful, but incisional biopsy and microscopic evaluation are mandatory for precise diagnosis.