Pure endoscopic endonasal removal of unusual anterior skull base aneursymal bone cyst extending to the frontal lobe.

Aneurysmal bone cysts (ABCs) are benign, nonneoplastic, hemorrhagic, and expansile osseous lesions that present most frequently at age younger than 20 years. Aneurysmal bone cysts typically involve long bones of extremities, thorax, pelvis, or spinal column. Skull base involvement is very rare. The authors report the case of a 23-year-old woman with ABC of the skull base and total removal of lesion with pure endoscopic endonasal approach. The patient had presented with nasal obstruction for 6 months. Physical and neurological examination findings were normal except for bilateral anosmia. Cranial magnetic resonance imaging (MRI) revealed a tumor occupying ethmoid sinuses anterior skull base that extended into bilateral frontal lobes. The patient underwent pure endoscopic endonasal surgery, and the tumor was resected gross-totally. Histologic examination revealed ABC. Consequently, ABC should be considered in differential diagnosis of skull base pathologies. Endoscopic endonasal surgical approach is a safe, minimally invasive, and effective way in the treatment of these tumors.