Paraffin sections show a moderately cellular dural-based tumour. Tumour cells have moderately pleomorphic round and oval nuclei with vesicular chromatin and a moderate amount of clear cytoplasm containing varying amounts of glycogen.
Cell boundaries are poorly demarcated. There is a discernible syncytial arrangement of tumour cells in many areas. No mitotic figures or areas of necrosis are identified.
Immunohistochemistry shows strong membrane staining in tumour cells for epithelial membrane antigen (EMA) (not shown) and somatostatin receptor (SSR2). There also patchy moderate nuclear staining for progesterone receptor (PgR) (not shown).
The features are of clear cell meningioma (WHO Grade II). The topoisomerase labelling index is approximately 8%.
FINAL DIAGNOSIS:
Clear cell meningioma (WHO Grade II).