Animation of Tumor Cells Extravasating Through Angiopellosis and Diapedesis. This animation illustrates the basic difference in mechanism of angiopellosis versus diapedesis extravasation. In the angiopellosis panel (left), the circulating tumor cell travels through the blood vessel and attaches to the endothelial lining of the vasculature. The membrane projections of endothelial cells then actively cover the tumor cell, prompting the expulsion of the cell into the surrounding tissue. In the diapedesis panel (right), the circulating tumor cell travels through the blood vessel and extravasates by squeezing through the endothelial cells of the blood wall.