Fibrous dysplasia with secondary aneurysmal bone cyst-a rare case report and literature review.

Introduction: Fibrous dysplasia (FD) and aneurysmal bone cyst (ABC) are uncommon non-neoplastic intraosseous lesions, and the occurrence of concomitant FD and ABC is extremely rare.

Case Report: An 11-year-old boy presented with gradual progressive enlargement of his right zygomatic bone over 4 years prior to presentation. Computed tomography revealed a lesion with a central bony area showing a ground-glass appearance surrounded by a well-defined expansile lesion with internal septations. An incisional biopsy was performed and suggested a fibro-osseous lesion. Resection was performed, followed by immediate reconstruction using autogenous bone graft from the iliac crest. Histopathological examination revealed irregularly shaped trabeculae comprising immature woven bone in a fibroblastic cell-rich stroma. Blood-filled sinusoidal spaces lined by fibrous septa containing scattered multinucleated giant cells were observed peripherally. These findings were compatible with concomitant FD and ABC. The patient was disease-free at the time of his 10-month follow-up.

Conclusions: Based on our literature search, this report is the first to describe concomitant monostotic FD and ABC in the zygomatic bone. Accurate diagnosis requires careful investigation and examination of clinical, radiographical, and histopathological features. The treatment of choice should provide an esthetic and functional improvement in the patient.