Cancer has, until very recently, been regarded as a collection of diseases characterized by, indeed defined by, abnormalities in cell division (mitosis). This is logical in that the most obvious attribute of most cancers is the formation of masses, called tumors, and the cancer cells found in tumors clearly arise by mitosis. But this is only a part of the story. Much recent evidence points toward another characteristic of cancer that might be as or even more important: abnormal cell mobility. In fact, fro…