A Rare Case of a Solid Variant Aneurysmal Bone Cyst of the Medial Sphenoid Bone: Clinical Features, Diagnostic Points, and Treatment.

A 5-year-old boy presented to our hospital with ptosis and an abnormal ocular position. Magnetic resonance imaging showed a well-defined mass measuring 20 mm in diameter in the medial sphenoid bone extending to the orbit and compressing the external ocular muscle. The patient underwent total surgical excision and was subsequently diagnosed with a solid variant of aneurysmal bone cyst via molecular integrated diagnosis. Solid variant of aneurysmal bone cyst is an extremely rare subtype of aneurysmal bone cyst, accounting for 0.2% of all primary bone tumors. It is characterized by the absence of a solid cystic component, which is difficult to diagnose via conventional hematoxylin and eosin staining. Molecular analyses revealed that this subtype is also characterized by the rearrangement of USP6 and the absence of the H3F3A mutation. This report discusses the clinical features of this extremely rare neoplastic lesion, the importance of an integrated diagnosis, and treatment options.