Non-small-cell lung carcinoma tumor growth without morphological evidence of neo-angiogenesis

Neoplastic growth is usually dependent on blood supply, and it is commonly accepted that this is provided by the formation of new vessels. However, tumors may be able to grow without neovascularization if they find a suitable vascular bed available. We have investigated the pattern of vascularization in a series of 500 primary stage I non-small-cell lung carcinomas. Immunostaining of endothelial cells has highlighted four distinct patterns of vascularization. Three patterns (which we called basal, papillary, and diffuse) have in common the destruction of normal lung and the production of newly formed vessels and stroma. The fourth pattern, which we called alveolar or putative nonangiogenic, was observed in 16% (80/500) of the cases and is characterized by lack of parenchymal destruction and absence of both tumor-associated stroma and new vessels. The only vessels present were the ones in the alveolar septa, and their presence highlighted, through the whole tumor, the lung alveoli filled up by the neoplastic cells. This observation suggests that, if an appropriate vascular bed is available, a tumor can exploit it and grows without inducing neo-angiogenesis. This could have implications for strategies aimed at inhibiting tumor growth by vascular targeting or inhibition of angiogenesis.