Xanthomatous changes in atypical and anaplastic meningiomas. Light and electron microscopic investigations.

Xanthomatous changes may occur in meningiomas of different histological type, however their incidence in combination with histological features of atypical or anaplastic meningioma has not been previously documented. In this report we present clinicopathologic, immunohistochemical and ultrastructural studies in the surgical cases of two atypical and three anaplastic meningiomas exhibiting prominent xanthomatous changes. In all tumors the xanthomatous cells were seen in association with typical meningioma structures such as meningothelial whorls or psammoma bodies as well as within the tumor parts displaying pleomorphism, patternless growth, increased cellularity, presence of necroses and mitoses or brain invasion. Ultrastructural study revealed a wide-range of lipid-containing cells, reflecting a continuum of gradual transition between polymorphic meningioma cells and xanthomatous cells. Commonly, the lipidized cells exhibited different degrees of plasmalemmal interdigitations and desmosomal junctions. Our study allowed us to confirm the meningothelial origin of xanthomatous cells in atypical and anaplastic meningiomas. Moreover, the ultrastructural observations of lysosomes in the majority of xanthomatous cells and the immunoreactivity for the CD68 antigen indicated their macrophage characteristics. It seems that a mixed meningeal/macrophage nature of xanthomatous cells can be related to the functional and structural multipotentiality of the primary leptomeningeal cells.