Tentorium cerebelli meningioma
Patient referred for evaluation of a posterior fossa lesion seen on the previous CT (not available).
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There is a solid lesion on the right superior aspect of the posterior fossa keeping a broad base within the tentorium cerebelli, but also with a doubtful invasion of the adjacent cerebellar folia on the multiplanar reformatted images. The lesion is isointense on T1 and hyperintense to the cerebral cortex on T2; it shows a bright contrast enhancement and mild homogeneous restricted diffusion.
This case raised some discussion among the radiology team whether the lesion was intra or extra-axial. By the general radiographic features and in a straightforward approach it looks to be an extra-axial tumor, most likely a meningioma. However, when approaching it with more caution and using reformatted plans, the lesion shows the involvement of the adjacent cerebellar folia, some of them seeming to be thinned and invaded/involved by the tumor; these features raised the concern about the possibility of an intra-axial lesion, such as metastasis.
The patient has no history of known previous malignancy.
After surgery, the lesion was confirmed as a meningioma.
- Bone: The section shows fragments of unremarkable lamellar bone. No evidence of tumor is seen.
- Tumor: The section shows fragments of a moderately hypercellular meningioma. This has a vague syncytial architecture. Tumor cells show moderate nuclear pleomorphism. No mitotic figures or areas of necrosis are identified and there is no evidence of brain invasion.
DIAGNOSIS: Meningioma (WHO Grade I).