The interaction between circulating tumor cells and the vascular wall is a crucial step in the process of extravasation of these cells and in the subsequent formation of the metastasis. Tumor cells extravasation is believed to be similar to that of leukocites across the vascular wall during inflammation. It has been documented that initial interaction of leukocytes with endothelial surface is characterized by their rolling over the cell surface, which can be followed by firm adhesion of the cells to the vessel wall. It is believed that in some conditions adherent cells can migrate across the endothelial layer and extravasate within the vascular wall (1 –4 ).
