[Pseudopsammoma bodies in meningotheliomatous Meningioma histochemical and ultrastructural study (author's transl)].

In 1938, Cushing and Eisenhardt first described one case of meningotheliomatous meningioma with intracellular “hyaline inclusion”, later named pseudopsammoma bodies by Kepes. The meningiomas with pseudopsammoma bodies belong to a very rare entity, and were described in only five previous reports. The present case was a 41-year-old female with a short history of convulsive disorder. Precontrast CT scan disclosed a high density mass in the right sphenoidal ridge and a contrast study showed marked enhancement. Neuroradiological examination including right carotid angiography demonstrated findings compatible with a sphenoidal ridge meningioma. A front-temporal craniotomy was performed and the mass was removed totally. Microscopic examination disclosed that the tumor was composed of whorls of meningotheliomatous cells and that many tumor cells contained intracellular eosinophilic and round or oval shaped inclusions. Histochemically, the inclusions were PAS-positive, diastase and neuraminidase resistant, and conjugated with concanvalin A (Con A). These staining reactions suggested that the inclusions were composed of glycoprotein, as previously reported by Kepes and others, and that they had mannose or glucose as receptors of Con A. Macrophages were seen to infiltrate around tumor cell clusters, and showed phagocytosis of the inclusion bodies. Some metachromasia was also observed. Electron microscopically, these substances were located in the intracellular spaces lined by microvilli, and numerous well-developed desmosomes were found at the intercellular junctions. These characteristics are quite similar to those of pleural mesothelioma, and suggested some relationship between normal meningeal cells and mesothelial cells in oncogenetic and anatomic aspects. In earlier reports, the substances were said to be secretory products and a possibility of meningioma cell differentiation to secretory cells was postulated. The results of the present study with Con A staining strongly support this opinion.