Omental immune aggregates and tumor metastasis within the peritoneal cavity

The omentum, an important peritoneal tissue, is studded with a high number of immune aggregates, or “milky spots,” the number, function, and phenotype of which is largely unknown. We have analyzed the immune composition on the normal omentum and also have shown that both free immune cells and tumor cells in the peritoneal fluid bind preferentially to these immune aggregates. This binding may be mediated by the network of collagen I fibers, which overlay these areas. In addition, we have shown that not only do omental vessels express vascular endothelial growth factor receptor 3 (VEGFR3), a receptor that is only found on angiogenic blood vessels, but that tumor cells co-localize with these vessels, possibly increasing the ability of tumor to induce neovascularization and therefore thrive.