Meningioma - intraventricular
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There is a large, vividly and homogeneously mass lesion, part of it appears intraventricular within the trigone of right lateral ventricular and a large part in the adjacent right parietal lobe. The mass is well defined, associated with a significant positive mass effect in the form of mid-line shift into the left side, dilatation of the left lateral ventricle and entrapment of the ipsilateral right sided temporal horn.
Surrounding the mass, is a large area of white matter hypodensity in the right frontal, parietal and temporal lobes, most in keeping with vasogenic edema.
Interpretation: Imaging differential diagnosis are: intraventricular meningioma with brain parenchymal extension. Primary CNS lymphoma is also a possibility.
Specimen labelled "intraventricular tumour": Atypical meningioma, predominantly fibroblastic, with brain invasion.
Final Diagnosis Comment:
The main features are those of a meningioma, predominantly of the fibroblastic type. In view of the mitotic figures, areas of necrosis, hypercellularity, and prominent nucleoli, this intraventricular tumour is best designated as an "atypical" meningioma.
The tumour invades brain. The appearance of the brain with clusters of cells with round nuclei and anuclear zones with microcystic change is reminiscent of a subependymoma. Thus, the possibility of there being two co-existing intraventricular tumours (meningioma and subependymoma) should be considered. It is also possible the findings in the brain tissue are reactive ependymal/subependymal changes.
Sections show a meningioma comprised of cells with elongated to round nuclei and eosinophilic cytoplasm with ill-defined cell boundaries. There is extensive collagen deposition within the tumour. Most of the tumour nuclei are rather large and show prominent nucleoli. Mitotic figures are seen within the tumour and usually number approximately 1-3 per 10 high-power fields. However, at least one area shows six mitotic figures per 10 high-power fields. There are a few areas of microscopic necrosis. In some areas the nuclei are quite crowded. In some regions there is a tendency to whorl formation and there are areas with psammoma body formation.
At the periphery of the tumour, fragments of brain are evident. In these fragments of brain there are clusters of cells with rounded nuclei and anuclear zones. Microcystic areas are also evident in these regions.
Immunohistochemistry shows the meningioma is positive for vimentin and focally positive for epithelial membrane antigen, and negative for keratin. There is intense positiviy in the brain for glial fibrillary acidic protein (GFAP)and some process positivity for vimentin and keratin. The meningioma shows scattered MIB1-positive nuclei, whereas the brain tissue shows only occasional positive nuclei.