[Ultrastructural study of meningiothelial meningioma with 'hyaline inclusions' (author's transl)].

One case of meningiothelial meningioma with "hyaline inclusions" (colloid-bodies or pseudopsammomas) as noted by Cushing and Eisenhardt (1938) and by Kepes (1961-1975) is reported by light and electron microscopy. Two types of these structures, either homogeneous or polymorphic, surrounded by microvilli are described and regarded as signs of secretory differentiation of tumor cells. In addition to Kepes' description, the authors show, at high magnification, the polymorphic material including homogeneous component, lamellar structures, microvesicles and dense bodies. The endocellular overproduction of the various types of "hyaline inclusions" and the nature of their material are discussed.