Syncytial neoplastic cells form vague whorls around vessels, separated by a more spindled fibrous component.
A touch prep demonstrates sheets of cells with indistinct cell borders and monotonous nuclear features.
Fascicles of spindled cells are similar to the fibrous variant.
The cells stream and whorl around hyalinized vessels.
The cellular features are bland and not concerning for atypical meningiomas, which can arise in any of the variants. Nucleoli are not especially prominent, pleomorphism is minimal, necrosis and increased mitotic figures are not present, and there is no invasion of the brain or dura.
EMA positivity is focal. Meningiomas are almost 100% for vimentin and focally positive for cytokeratin and EMA.
Transitional (mixed) meningiomas are a combination of the two more common or conventional meningiomas variants.
Histologically, there is a blend of the meningotheliomatous and fibrous variants. Similar to its constituents, the transitional variant is considered a WHO Grade I tumor.