So basically, in order to move, a cell climbs hand-over-hand along the extracellular matrix until it reaches a blood or lymphatic vessel and penetrates it. From there, it’s smooth sailing. By the way, the thinner walls of lymphatic vessels are easier to penetrate, which is why examining lymph nodes plays a major role in cancer detection. The trick then, is not only to figure out all the factors that affect the chemical reactions that enable cells to move around, but also to figure out how to control these reactions selectively. Because cell movement is necessary for healing wounds and fighting off diseases, stopping it completely isn’t an option. Instead, scientists will have to figure out how to block movement in select locations, like in the extra-cellular matrix around growing tumors.