Case report MedInform ISSUE 1, 2019 987 MedInform Aneurysmal bone cyst of the mandible, mimicking follicular cyst Zornitsa Mihaylova, Pavel Stanimirov, Evgeniy Aleksiev Dept. of Dental, Oral and Maxillofacial Surgery, Faculty of Dental Medicine, Medical University – Sofia; Maxillofacial Surgery Clinic, Alexandrovska Hospital; Abstract Aneurysmal bone cyst (ABC) is a rare benign, non-odontogenic osteolytic lesion of the jawbones. Commonly the clinical presentation consists of pain, significant bone expansion and facial asymmetry. We report a case of a 14-year-old asymptomatic patient, with aneurysmal bone cyst, identified on a routine X-ray, mistaken with dentigerous cyst. Thorough surgical removal of the cystic lesion was carried out, followed by histopathological examination confirming the diagnosis. Long term follow-up showed no complications or recurrence. Keywords: aneurysmal bone cyst, osteolytic lesions, bone cysts, non-odontogenic cysts Introduction Aneurysmal bone cyst (ABC) is a relatively rare non-neoplastic osteolytic lesion. Significant bone expansion is commonly observed. It consists of varying in size serum- or blood-filled spaces separated by trabeculae. The spaces may contain osteoid tissue and osteoclast-like giant cells (1). ABC has been first described in 1893 by Van Arsdale as an ossifying hematoma (2), while the first case identified in the jaws has been reported by Bernier and Bhaskar in 1958 (3). ABCs primarily affect the long bones and vertebrae, with only 1% to 3% incidence in the jaws (3). The mandible is more commonly affected than the maxilla, with a ratio of 2:1, usually found in the posterior DOI: 10.18044/Medinform.201954.987