Aneurysmal Bone Cyst of the Sphenoid Body Mimicking Craniopharyngioma: A Case Report

An aneurysmal bone cyst is a locally destructive benign lesion that predominately affects the long bones. Sphenoid body involvement is rare. To date, only 19 primary aneurysmal bone cysts of the sphenoid body have been reported. We describe the case of an 18-year-old male with a one-week history of severe right eye pain and lacrimation, right-sided diplopia, right-sided headache, photophobia, nausea, and vomiting. Magnetic resonance imaging (MRI) demonstrated a lobulated lesion centered in the sphenoid body with expansion into the cavernous sinus, sellar region, and clivus. The lesion had a homogenous hyperintense T2 signal with enhancing sidewalls and minimal septations. Computed tomography (CT) angiography revealed a hypoattenuating lesion containing a substance of nine Hounsfield units, compatible with water density. The clinicoradiologic findings were consistent with a craniopharyngioma. Intraoperatively, the lesion was confirmed to contain clear fluid and have prominent arterial feeding vessels. The extradural tumor was then excised with intralesional curettage. The histopathologic analysis resulted in a diagnosis of an aneurysmal bone cyst. This case highlights the potentially non-specific and variable appearance of aneurysmal bone cysts and the need to consider it in the differential diagnosis of sphenoid bone lesions.