Widely invasive solitary fibrous tumor of the sphenoid sinus, cavernous sinus, and pituitary fossa.

Solitary fibrous tumor is a spindle cell tumor first described in the pleura, but also found in multiple extrathoracic sites including the meninges, orbit, nasal and paranasal sinuses. No cases have been previously reported in the cavernous sinus or pituitary fossa. We present the case of a 54-year-old woman who presented with progressive amaurosis. On imaging studies, a widely infiltrative lesion involving the pituitary fossa, sphenoid sinus, cavernous sinus, carotid artery, medial temporal, ethmoid, and pterygoid bones, and extending into the nasopharynx was discovered; impression was a malignant tumor originating in the pituitary fossa. At surgery, the tumor was only partially resectable because of extensive bony invasion and encasement of the carotid artery, and was found to compress but not invade the pituitary gland. Histology showed a spindle cell proliferation with a dense, hyalinized collagenous stroma and dilated vascular spaces, some showing a staghorn-like appearance. Areas of cellular pleomorphism and increased cellularity were present, but few mitoses were identified. Immunohistochemistry showed strong positivity with CD34, factor XIIIa, CD99, and Bcl-2. There was scattered cyclin D1, mib-1, and p53 positivity. Muscle, epithelial, vascular, and melanocytic markers were negative. These results led to the diagnosis of solitary fibrous tumor. The size, extensive invasion, and bony destruction indicated a tumor with at least low malignant potential. The occurrence of solitary fibrous tumors in the pituitary fossa and sinuses of the head and neck is rare, but must be considered in the differential diagnosis of spindle cell lesions in these regions.