Rhabdoid meningioma

Overlying the left frontoparietal region there is a large extra-axial lesion that is slightly hypointense relative to grey matter on T1 and iso to hyperintense to grey matter on T2. There is mass effect with compression of the underlying sulci and a small contralateral midline shift. The lesion demonstrates moderate but slightly heterogeneous contrast enhancement. There is also dural enhancement and dural tail. Minimal subjacent white matter T2 hyperintensity but no significant vasogenic edema. Medially the mass abuts the superior sagittal sinus which is not occluded or overtly invaded. Several prominent flow voids are noted within the mass. No invasion of the overlying bone and no significant hyperostosis. Incidental left middle cerebellar peduncle developmental venous anomaly. Nonspecific high T2 signal foci are noted in the white matter. The midline structures are unremarkable.

Frameless post-contrast CT brain performed to assist surgical approach. The large left frontoparietal vivid enhancing mass consistent with meningioma again noted.

Since the previous study (not shown), there has been unequivocal disease progression. Once again, there is a combination of gliosis and vasogenic edema. There is a narrowing of the superior sagittal sinus but maintained flow voids are noted, unchanged compared to previously. This is well demonstrated on the axial T2 imaging. Susceptibility artefact is once again noted in the surgical bed. There is no further enhancing lesion noted.

MICROSCOPIC DESCRIPTION: 1&2. Paraffin sections show a dural-based densely hypercellular meningioma. Tumor cells have a diffuse sheeted arrangement and the majority have rhabdoid cytological features - strap-like and epithelioid cells with pleomorphic round and oval vesicular nuclei and a large amount of densely eosinophilic cytoplasm. Frequent mitotic figures are identified (14 in 20HPF). Several microscopic foci of necrosis are noted. There is no evidence of brain invasion. Immunohistochemistry shows patchy moderate membrane staining in tumor cells for epithelial membrane antigen (EMA). No nuclear staining for progesterone receptor (PgR) is seen. The topoisomerase labeling index is approximately 35%. The features are of rhabdoid meningioma (WHO Grade III).

DIAGNOSIS: 1&2. Brain tissue: Rhabdoid meningioma (WHO Grade III).