Secondary aneurysmal bone cyst arising from polyostotic craniofacial fibrous dysplasia.

Fibrous dysplasia (FD) is a benign condition affecting osteoblasts, which fail to undergo proper differentiation and maturation, resulting in the replacement of normal osteoid matrix with ground glass fibrous tissue. Aneurysmal bone cyst (ABC) is a benign, expansile, lytic lesion characterized by multiple blood-filled cystic cavities containing haemorrhagic products at varying stages. Secondary ABC arising from craniofacial FD is extremely rare. To date, only 10 cases have been reported in the literature. This report highlights the clinical presentation, imaging findings, and histopathological confirmation of a secondary ABC in a patient with polyostotic craniofacial FD.