Meningothelial meningioma with abundant oedema
Confusion, vomiting and urinary incontinence.
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Enhancing hyperdense mass in the left anterior cranial fossa measures ~4cm in diameter. This is broad-based to the left side of the olfactory groove and planum sphenoidale inferiorly. There is the suggestion of minimal hyperostosis at the interface between bone and tumour.
Surrounding the lesion there is extensive hypoattenuation in the white matter of the left frontal lobe extending into the corpus callosum, anterior limb left internal capsule, and left external capsule.
There is extensive mass-effect with diffuse sulcal effacement in both hemispheres, subfalcine and uncal herniation, and 1.3 centimetres of midline shift to the right. The left lateral ventricle and third ventricle are almost completely effaced. There is dilatation of the body, trigone, and temporal horn of right lateral ventricle.
No evidence of acute haemorrhage or acute infarction.
Large left anterior cranial fossa mass. Given the broad contact with the skull base is most probably extra-axial, although a rim of grey matter surrounding the tumour is not seen.
Olfactory groove meningioma is considered most likely. Extensive white matter hypoattenuation probably represents vasogenic oedema although parenchymal invasion by aggressive meningioma is also a possibility.
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Large extra axial tumour with broad-based attachment to the planum sphenoidale and extension into the left olfactory groove. This is hyperintense to grey matter on T2, isointense on T1, with abnormally increased diffusion restriction, and bright homogeneous enhancement following contrast administration. There is a small enhancing dural tail at the left sphenoid.
Extensive mass-effect on both frontal lobes (left greater than right ). Almost complete effacement of the left lateral ventricle and third ventricle. Mass effect on the midbrain. 1.1 cm of midline shift to the right. Diffuse sulcal effacement in both hemispheres.
Extensive vasogenic oedema surrounding the tumour: in the left frontal lobe extending into the anterior corpus callosum and left insula.
There is entrapment of the right lateral ventricle with surrounding FLAIR hyperintensity indicating transependymal fluid shift.
The A2 and A3 segments of both anterior cerebral arteries are displaced to the right by the mass.
No intracranial aneurysm or evidence of steno-occlusive disease.
The patient went on to have a resection.
MICROSCOPIC DESCRIPTION: The sections show a moderately hypercellular meningioma. This has a well developed syncytial architecture. Tumour cells show mild nuclear pleomorphism. Scattered mitotic figures are identified (3/10 HPF). No areas of necrosis are identified and there is no evidence of brain invasion.
FINAL DIAGNOSIS: Meningothelial meningioma (WHO Grade I).
This case illustrates an important point about garden variety meningothelial meningiomas; although it is true that oedema within the adjacent brain is seen in tumours with brain invasion (i.e atypical (WHO grade II) or anaplastic (WHO grade III) tumours) it is also frequently seen in benign (WHO grade I) tumours and other grade II tumours (e.g. clear cell meningioma) without brain invasion. As such, especially given how much more frequent grade I tumours are, presence of oedema should not be used to predict higher grade.