Atypical meningioma (WHO grade II)
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There is a large left frontal region extra-axial mass of variegated density and heterogeneous contrast enhancement. The mass demonstrates some small hyperdense foci in its periphery that may represent calcifications. The mass exerts positive mass effect upon the left cerebrum narrowing of the left interhemispheric fissure and with minor rightward subfalcine herniation.
Large enhancing left frontal extra-axial dually based mass remodelling inner table, almost certainly a meningioma. Differential includes hemangiopericytoma.
The patient went on to have a resection.
MICROSCOPIC DESCRIPTION: The sections show a moderately cellular meningioma with focal infiltration into the attached dura. The tumor forms whorls and fascicles. No sheeting arrangement is seen. The tumor cells have enlarged nuclei and prominent nucleoli. There are up to 8 mitoses per 10 high-power fields. Scattered small foci of necrosis are noted.
There is no brain parenchyma included. No malignant change is seen. The features are those of an atypical meningioma. The Ki-67 index is about 25%. Most of the tumor cells are progesterone receptor negative (about 5% positive).
FINAL DIAGNOSIS: Atypical meningioma (WHO Grade II).