Patient with basal cell carcinoma (BCC) being treated with imiquimod cream. The topical skin drug is put on each night and left on for eight hours. The course of treatment is for six weeks. BCC is the most common form of skin cancer among fair-skinned people. It mostly affects the elderly, although in recent years the average age of onset has steadily decreased. It usually appears on the face and is thought to be caused by the ultraviolet radiation in sunlight. It slowly destroys surrounding tissue, but seldom spreads to other parts of the body.