Migrating cancer cell. Coloured scanning electron micrograph (SEM) of a migrating, or metastasing, cancer cell. Only the nucleus (right, pale pink) and actin cytoskeleton (threads) are seen, other cell constituents have been removed. The cytoskeleton allows for directional movement of the cell by forming actin-filled processes (at left), that the rest of the cell follows. The movement of cancer cells around the body (metastasis) is an important part of a cancer's malignancy.