Presentation
Left upper limb weakness and partial seizure.
Patient Data
Large, enhancing right frontal extra-axial tumor with invasion through the right frontal bone into the scalp soft tissues. There is mass effect on the right frontal lobe, with a small amount of adjacent edema, and partial effacement of the frontal horns.
Large, enhancing right frontal extra-axial tumor with invasion through the right frontal bone into the scalp soft tissues. The mass has some cystic components. There is mass effect on the right frontal lobe, with a small amount of adjacent edema, and partial effacement of the frontal horns.
The patient proceeded to surgery.
Histopathology
MICROSCOPIC DESCRIPTION: The sections show a meningioma with increased cellularity. The tumor forms solid sheets as well as scattered whorls. The tumor 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 tumor 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 tumor 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 tumor cells are weakly progesterone receptor positive.
DIAGNOSIS: Atypical meningioma with full thickness invasion into skull bone (WHO Grade II).
Case Discussion
Atypical meningiomas (WHO grade II) are more aggressive than WHO grade I meningiomas with a much higher recurrence rate (~40% vs ~12%). Imaging cannot reliably differentiate between the two.