[Electron microscopic observations of blood vessels in ependymoma]

The findings of an ultrastructural study of the blood vessels and their surrounding structures in ependymoma are demonstrated. Six surgically removed cases of ependymoma are investigated. The lumen of the blood vessels, especially in vascular rosettes is often wider than those of normal brain capillaries. The endothelial cells are structurally varied, but sometimes attenuated in many areas. Also, they often have several fenestrations. Moreover, they have increased pinocytotic vesicles and filaments, and contain occasional Weibel-Palade bodies, multivesicular bodies and other cytoplasmic organelles. The perivascular space is often wide, especially in intraspinal ependymoma, and filled with multiple layers of basal laminae permeated by electron, dense fluids. There are also collagenous fibers and Luse bodies. Basal lamina covering tumor cell surfaces is more distinct than other basal laminae. The tumor cells facing the blood vessel interestingly show structures similar to those of astrocytic vascular feet. The fenestration in the endothelial cells probably has an important role in the increased vascular permeability of ependymoma.