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Ultrastructure of psammoma bodies of meningioma in tissue culture.

An 8-day-old tissue culture of a human meningioma was studied by electron microscopy. Psammoma bodies were detected in all stages of evolution, affording a unique opportunity for observing the genesis of these structures. Matrix vesicles appeared instrumental in the calcification of a granular extracellular material. Although matrix vesicles are described in both physiologic and pathologic calcification, they have not been previously reported in the very few ultrastructural studies of psammoma bodies in meningiomas.