The patient underwent to a surgical resection.
The sections show a meningioma with increased cellularity. The tumour forms solid sheets as well as scattered whorls. The tumour cells have enlarged and mildly pleomorphic nuclei with focal prominent nucleoli. There are up to 16 mitoses per 10 high power fields. Areas of necrosis are seen. Cerebral cortex is present and there is no evidence of brain invasion. The tumour invades through the dura into the skull bone. It involves the entire thickness of the bone through the cortex and it is 0.1mm from the outer periosteum. The tumour involves the circumferential radial bony margin. There is no evidence of malignant change. The features are those of atypical meningioma. The Ki-67 index is about 20%. About 10% of the tumour cells are weakly progesterone receptor positive.
Atypical meningioma with full thickness invasion into skull bone (WHO Grade II).