QUANTITATIVE COMPARISON OF THE MORPHOLOGY OF THE MICROVASCULATURE OF PRIMARY LUNG LESIONS AND METASTATIC BRAIN-TUMORS

Endothelial cells that make up microvessels display a differential exp ression of structure and function that allows them to meet the require ments of the tissues they vascularize. The growth of tumours requires neovascularization that occurs by angiogenesis, a process by which new capillaries are formed from existing vessels. It has been proposed th at the local environment determines the morphological characteristics of the vessels that vascularize it. The present study is a quantitativ e investigation of the properties of capillaries that may contribute t o their permeability and their general morphology. Tissue samples were taken from primary non-small cell lung carcinomas and from the same t umour type that had metastasized to brain. Normal samples were taken f rom tissue distant from the site of pathology. Using transmission elec tron microscopy, profiles of capillaries from the tissue samples were examined and photographed. Image-analysis was performed to measure ves icular and mitochondrial density, vessel size and vessel wall thicknes s. The results showed that the morphology of the capillaries that vasc ularize the primary lung rumours differs from the morphology of the ca pillaries that vascularize the metastases of these tumours in the brai n. In addition to differences in the quantitative observations, qualit ative differences were observed with respect to the presence of fenest rations in the vessel wall, found only in brain tumour vessels, and th e presence of 'open' junctions, seen only in lung tumour vessels. Thes e results suggest that although the environment of the tumour changed the morphology of the vessels so they were no longer normal, it did no t have the same effect on the vessels that vascularize it at the two d ifferent sites. Therefore, the response of microvessels in the host ti ssue to factor(s) produced by tumour cells may be multifaceted and dep endent upon the properties of local vessels.