Mixed colloid cyst-xanthogranuloma of the third ventricle. A light and electron microscopic study.

A mixed colloid cyst-xanthogranuloma of the third ventricle is described. The xanthogranuloma associated with the cyst completely occupied the third ventricle. On light microscopy, a single epithelial layer with a basal lamina was seen lining the cyst wall. Electron microscopic study revealed three different kinds of cells in the epithelial layer: ciliated, nonciliated, and basal cells. Many lipid droplets were present in the superficial epithelial cells, macrophages, pericytes, and endothelia. The pathogeneses of the cyst and of the xanthogranuloma are discussed.