Cellular transmigration is a type of cell migration (most often leukocytes or tumor cells) through the vascular endothelium due to a chemo-attractant. Transmigration tests measure the interactions between leukocytes or tumor cells and the endothelium and the transmigration of these cells through the endothelium. This type of test uses the principle of the Boyden chamber in which the endothelial cells are seeded to form a monolayer before adding the cells of interest capable of migrating.
The initial arrest and fixation of tumor cells to the vascular endothelium precedes extravasation from the blood stream and is a crucial step in the metastatic cascade of the tumor. The extravasation of tumor cells is equivalent, in many ways, to the entry of leukocytes into the inflammatory tissue. Leukocyte extravasation consists of multiple consecutive processes including capture of circulating leukocytes, subsequent leukocyte rolling, arrest, firm adhesion, and transmigration.