The sections show a moderately cellular tumor. The tumor forms fascicles and bundles, intermixed with collagenous tissue in the background. No whorls are seen. The tumor cells have ovoid nuclei with no nuclear pleomorphism. Occasional mitoses are noted (less than 4 per 10 high power fields). Scattered staghorn type blood vessels are present. There is one area of brain invasion, with tumor infiltrating into the neuropil. 

DIAGNOSIS: Brain tumor: Solitary fibrous tumor.

Comment: No grading has been given in the WHO classification. Most behave in a benign fashion. However, there is brain invasion in this biopsy and its significance is unclear. No other adverse histological features are otherwise seen.