Skin cancer cell. Coloured scanning electron micrograph (SEM) of a squamous cell carcinoma cell. The many microvilli (small projections) on the cell's surface are typical of cancer cells. The larger projections (green) allow the cell to move and the cancer to spread (metastasis) around the body. Squamous cell carcinoma is the second most common form of skin cancer and affects cells in the upper layers of the skin. Most cases arise from pre-cancerous lesions known as solar keratoses, which are caused by sun damage.