OBSERVATION OF PSAMMOMA BODIES IN CULTURED MENINGIOMAS - ANALYSIS OF 3-DIMENSIONAL STRUCTURE USING SCANNING AND TRANSMISSION ELECTRON-MICROSCOPY

In contrast to the inner structure, three-dimensional structure of psa mmona bodies in meningiomas is not well defined. This study examined t hree cultured meningiomas, in which surface observation of psammoma bo dies might be easier than in the tumor tissues since influence of inte rposing connective tissue is minimized in tissue culture. Early cultur e revealed that psammoma bodies with frank calcification were suspende d in the tissue culture medium, and so were they collected, centrifuge d, and then processed for electron microscopy. Ultrastructurally, psam moma bodies were mostly spherical in shape and composed of a core of d ense calcification and surrounding collagen fiber bundles. Apart from psammoma bodies, round bodies with concentric lamination like a transv ersely cut onion were frequently noted by light microscopy. These bodi es were composed mainly of tangles of collagen fibers emerged from sur rounding tumor cell processes. The results suggest that psammoma bodie s in meningiomas arise in part from meningothelial whorls due to colla gen production by tumor cells followed by obliteration and disappearan ce of tumor cell processes, although some of the alternative pathways for psammoma body formation proposed by other investigators cannot be ruled out by this study.