Atypical presentation of a solid-variant orbital aneurysmal bone cyst with a literature review.

Introduction: Aneurysmal bone cysts (ABCs) are rare, rapidly expansile, benign, vascular lesions capable of causing local bone destruction. The majority of cases present as multi-cystic lytic lesions (with solid-variant ABCs representing<10% of all presentations) of the long bones or vertebrae, rarely occurring in the head/neck region.

Clinical Case: A 44-year-old female presented with nine days of worsening pain, ptosis and proptosis in the right eye. CT and MR imaging revealed a 3.2cm extra-axial multiloculated right frontal lobe mass in the orbit with fluid-fluid levels secondary to layering of solid blood components. A right craniotomy was performed and the lesion was resected piecemeal with subsequent high speed burring to remove residual tissue. Histological evaluation revealed spindle and giant cell infiltration of the bone without vascular channels. Based on these findings, the lesion was diagnosed as a solid-variant orbital ABC without paranasal sinus involvement. The patient recovered fully with no residual symptoms.

Conclusion: This case report details a rare presentation of ABC (solid-variant presenting outside of the vertebrae/long bones) with discussion concerning possible treatment modalities and guidance for follow-up.