Vascular and Extra Vascular Spaces in Tumors: Tumor Vascular Permeability

In rapidly growing mouse tumors observed through a transparent chamber, the blood vessels were found to reach a volume of 40 to 50% of total space within 5 to 8 days. The tumors elicited a production of new capillary endothelium from the host. Morphological studies of blood vessels in different human brain tumors showed alterations which might increase the trans vascular transport of different materials. Thus, fenestration, widened intercellular junctions, increase in pinocytotic vesicles, and infolding of the luminal surface were observed. In low-grade human astrocytomas and glioblastomas, similar observations were made, including increased overall vessel diameter and a greater number of endothelial cells, with a corresponding increase in the number of intercellular junctions. It was suggested that the vascular pattern observed in brain tumors could be interpreted as an active, hyperplastic response.