Vascular structures in brain tumors.

The blood vessels within brain tumors show alterations from the normal anatomy. Some of these seem to be related to an increased capacity to transfer materials between the lumen and the parenchyma and are probably intimately connected with the edema associated with the tumor. These alterations include fenestration, widened intercellular junctions, increase in pinocytotic vesicles, and infolding of the luminal surface. Other alterations are observed but their function is not as clear. The latter include an increase in the number of tubular bodies, the appearance of tubular structures within vacuoles, tubular arrays within the nuclear envelope and rough endoplasmic reticulum, and endothelial proliferation, among others.