Figure 1.

Schematic representation highlighting differences between blood vessels, lymph vessels, and VM structures. Differences are shown between an endothelial lined blood vessel (left side), a lymph vessel (center), and the hypothesized VM structure (right side). Blood vessels present an external layer of pericytes which overlay a basement membrane, with endothelial cells lining the luminal side. In lymph vessels, a similar architecture is present, however pericytes are absent and the basement membrane is thinner. Finally, the proposed structure present in VM has cancer cells sitting on the non-luminal side of a glycoprotein-rich (PAS+) matrix, with the total absence of endothelial cells.