The vasculature of experimental brain tumours. Part 2. A quantitative assessment of morphological abnormalities.

Two groups of the morphological abnormalities of brain tumour vasculature described in the previous paper (Deane and Lantos 1981) were quantified. First, blood vessel density, endothelial hyperplasia and endothelial cytology, 3 general features of the vasculature, were assessed, giving a score according to the Microscopic Angiogenesis Grading System (Brem et al. 1972). This not only gives information about the vascular supply of tumours but also often provides a reliable index of malignancy. The system was also adapted for electron microscopy. Secondly, 3 specific features of the endothelial lining were estimated: cytoplasmic vesicle content, fenestrations and abnormal endothelial intercellular junctions, which are thought to represent possible mechanisms of increased trans-endothelial transport. It was found that cytoplasmic vesicle content was 3--6-fold greater in tumour blood vessels than in capillaries from normal brain, and may therefore play an important role in cerebral oedema. However, fenestrations and abnormal endothelial junctions were infrequently seen, and were unevenly distributed.