Cranial aneurysmal bone cyst: a diagnostic problem. With a review of the literature.

Aneurysmal bone cysts (ABC) are benign osteolytic lesions that are more common in young people than in adults and involve the skull only exceptionally. The origin of ABC is still debated; indeed, some authors consider ABC to be an anomalous bony reaction that is secondary to traumas or tumours. Conversely, others consider ABC to be a distinct entity. A case of a healthy young female affected by a left frontal ABC is reported here. The clinical onset was characterised by the sudden appearance of a tender and mildly painful frontal mass. Neuroradiological assessment showed a well-circumscribed lytic lesion of the frontal bone with predominantly outward extension. En bloc surgical removal of the lesion was successfully achieved; a reconstructive cranioplasty was also performed to repair the cranial defect. The rarity of the condition described, together with the absence of clear guidelines, prompted us to review the more recent literature with the twin goals of identifying radiological features and becoming able to address the diagnosis and rules for treatment of such a rare entity.