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Occupying the right anterior cranial fossa/anterior aspect of the middle cranial fossa and extending across the midline into the left anterior cranial fossa, there is a lobulated mass measuring 8.8 x 4.0 x 7.1cm. This is slightly hyperintense to cortex on T1 and isointense to cortex on T2 and FLAIR, and demonstrates avid contrast enhancement. The mass is favored to be extra-axial. Within the mass, there is a rounded region of increased diffusion restriction (ADC = 650 x 10-6 mm2/s), possibly reflecting a region of higher cellularity. No invasion of the orbital apex. The right frontal lobe is compressed and demonstrates a large amount of edema. The right lateral and third ventricles are compressed and there is 26mm leftward midline shift with subfalcine herniation. No definite osseous invasion appreciated.
Large right frontal/anterior temporal mass with significant mass effect is favored to represent a meningioma. Hemangiopericytoma, and even less likely would be lymphoma in the differential disagnosis.
This patient went on to have a craniotomy and macroscopically complete resection.
MICROSCOPIC DESCRIPTION: Paraffin sections show a moderately hypercellular meningioma. A syncytial architectural pattern is discernible throughout the tumor. Tumor cells show moderate nuclear pleomorphism and there are scattered mitotic figures (2/20 HPF). The tumor is seen to have a pushing interface with underlying brain parenchyma but no evidence of brain invasion is seen. There are no areas of necrosis.
DIAGNOSIS: Meningioma (WHO Grade I).
Despite the WHO grade I histology, but inline with the radiological appearance, the tumor recurred rapidly at the resection margins (multiple 1.5-2cm diameter nodules) within a few months. This suggests that it is in fact a WHO II tumor, with perhaps sampling error or brain invasion not being evident.