Intracranial aneurysmal bone cysts in association with fibrous dysplasia: Case report and scoping review of case reports.

Background: Aneurysmal bone cyst (ABC) in association with craniofacial fibrous dysplasia (FD) is rare and may mimic aggressive change when a previously indolent lesion enlarges rapidly. We report an intracranial/cranial vault case and map published cranial vault/skull-base cases. Case Description: A 16-year-old girl presented with a rapidly enlarging left parietal mass, headache, intermittent diplopia, and vertigo. Magnetic resonance imaging demonstrated expansive craniofacial/skull-base FD with a multiloculated osteolytic parietal component containing hemorrhagic fluid-fluid levels, suggestive of ABC. Preoperative embolization was followed by resection and cranial reconstruction. Histopathology confirmed FD with a focal ABC component. At 3-year follow-up, the patient had no recurrence of the resected lesion. A scoping review was performed using structured PubMed/MEDLINE and Embase searches from database inception to December 2025, limited to articles in English or Spanish, including case reports/series of ABC in association with FD involving the cranial vault and/or skull base. Thirty-three individual cases were identified: 57.6% male, mean age 18.6 years (range 6-40). FD was polyostotic in 48.5%, monostotic in 24.2%, and unspecified in 27.3%. The frontal bone was the most frequent site (15.2%). The cystic ABC pattern predominated (75.8%). Follow-up was reported in 54.5% (mean 9.6 months among reported cases). Conclusion: ABC should be considered when craniofacial FD shows rapid enlargement, pain, neurological/neuro-ophthalmologic symptoms, or fluid-fluid levels. Diagnosis requires clinicoradiologic-pathologic correlation. Management should be individualized, often favoring embolization and maximal safe resection with reconstruction and long-term surveillance.