Solitary fibrous tumor of the pituitary

The pituitary fossa is enlarged and remodeled by a prominent hyperdense pituitary mass, presumably hemorrhagic. The nasal septum is somewhat deviated towards the right without large bony spurs. The sphenoid sinus is well aerated, divided unequally into a small right and large left side, which is further partially divided by left-sided septum.

A large soft tissue mass fills the enlarged pituitary fossa and extends superiorly into the suprasellar cisterns, where it elevates the optic chiasm. It measures 15 mm in anteroposterior diameter, 25 mm in height and 30 mm in width. It is of heterogeneous signal intensity, with low T2 signal and vivid contrast enhancement. It extends into the right cavernous sinus, but probably only laterally displaces the left cavernous sinus without definite MRI evidence of invasion. There is also a small anterior meningeal "tail" extending along the chiasmatic sulcus for a distance of 4 mm. 

Remainder of the imaged brain (please note this study has been targeted to the pituitary, and as such the whole brain has not been imaged) appears unremarkable. A few small scattered foci of abnormal signal within the white matter of the cerebral hemispheres may represent chronic small vessel ischemic disease.

Conclusion:

Large pituitary mass with moderate superior displacement of optic chiasm and invasion of the right cavernous sinus. Most likely this represents a macroadenoma with necrosis and hemorrhage although the absence of high T1 signal components is a little unusual. An anterior contrast enhancing "tail" is unusual for pituitary macroadenoma and a meningioma is not excluded, although appearances would be unusual (both morphology and signal intensity). 

Paraffin sections show a densely hypercellular tumor which appears to have an attachment to dura. Tumor cells have moderately pleomorphic round and oval nuclei with an open arrangement of chromatin and minimal cytoplasm and are admixed with haphazardly arranged bundles of collagen within a vascular stroma. No mitotic figures or areas of necrosis are identified. No normal pituitary parenchyma is included. Tumor cells show strong membrane immunostaining for CD34 and moderate staining for desmin. There is also strong staining for bcl-2 and CD99. A small number of tumor cells show moderately strong nuclear staining for progesterone receptor (PgR). No staining for synaptophysin, epithelial membrane antigen (EMA), thyroid transcription factor (TTF-1), S-100 protein, smooth muscle actin (SMA) or CD56 is seen in tumor cells. The features are of solitary fibrous tumor. The topoisomerase labeling  index is approximately 1%.

DIAGNOSIS:

Solitary fibrous tumor (WHO Grade I)