One of the adhesion molecules (embedded in the surface of the linings of blood vessels) that assists the neutrophils on their journey from the bloodstream through the walls of blood vessels (e.g., to combat pathogens into adjacent tissues). Tumor cells also exploit CD44 molecules in order to metastasize (spread throughout the body’s tissue from a single beginning tumor) via a similar (tumor cell)-through-blood vessel-wall adhesion molecule mechanism.