MICROSCOPIC DESCRIPTION: 1&2. Paraffin sections show a dural-based densely hypercellular meningioma. Tumour cells have a diffuse sheeted arrangement and the majority have rhabdoid cytological features - strap-like and epithelioid cells with pleomorphic round and oval vesicular nuclei and a large amount of densely eosinophilic cytoplasm. Frequent mitotic figures are identified (14 in 20HPF). Several microscopic foci of necrosis are noted. There is no evidence of brain invasion. Immunohistochemistry shows patchy moderate membrane staining in tumour cells for epithelial membrane antigen (EMA). No nuclear staining for progesterone receptor (PgR) is seen. The topoisomerase labelling index is approximately 35%. The features are of rhabdoid meningioma (WHO Grade III).
DIAGNOSIS: 1&2. Brain tissue: Rhabdoid meningioma (WHO Grade III).