The aneurysmal bone cyst (ABC) is a rare benign lesion with an incidence of approximately 1% to 2% of bone tumors mainly in patients of 10 to 20 years of age and requires an operative procedure involving complete removal.We present a rare case of a large ABC in the angle and ramus of the mandible of a 14-year-old boy. The lesion had first been seen by a pediatrician 3 months before and turned out to be causing both a large and rapidly increasing swelling of the right face. Histology revealed a solid ABC, located in the angle and ramus of the mandible with cortical perforation and extrusion of the neighboring structures. A segmental resection of the mandible and soft-tissue excision of the lesion was performed. The mandible was primarily reconstructed by microvascular free-fibula transfer.The ABC did not show specific clinical or radiologic signs based on varying clinical examinations. The diagnosis was thus challenging, and other malignant tumors that can occur in the maxillofacial field had to be considered. Aneurysmal bone cysts mainly occur in patients 10 to 20 years old, so it is of clinical significance for pediatricians and pediatric dentists, who may well be the first to see such patients. This case report shows an ABC unusual in both its clinical findings and the therapy necessary. This article gives a conclusive review of diagnosis, pathogenesis, and treatment options.