Migrating breast cancer cell. Coloured scanning electron micrograph (SEM) of a cultured breast cancer cell moving (metastasising) through two holes in a support film. Numerous fillipodia (thread-like) and surface blebs (lumps) can be seen. These features are characteristic of highly mobile cells, and enable cancerous cells to spread rapidly around the body, and invade other organs and tissues (metastasis). The cells may clump to form tumours. Breast cancer is the most common form of cancer in women. Magnification: x5000 when printed 10 centimetres wide.