Skin cancer is a very common malignant tumor of the skin. It occurs well in the exposed parts of the body, such as the face and limbs. In the population, the incidence rate is highest in middle-aged and old people, and it can also be seen in young people. The lesions can be primary or malignant from benign lesions such as pigmented nevi. Primary lesions may appear as fast-growing dark brown or black skin plaques or nodules, chronic ulcers of the skin, and so on. The lesions are usually irregular, infiltrated, feel “dirty” and have a non-smooth surface. Benign lesions should be considered to be cancerous if they: 1. Grow suddenly faster. 2. Sudden deepening of color or uneven color. Repeated spontaneous ulceration at the lesion. Prevention and treatment methods include the following: 1. Avoid excessive ultraviolet radiation. 2, often eat foods with a lot of vitamins and antioxidants. Such as purple kale, green cauliflower and so on. 3.Tune up your emotions and be in a happy mood. 4, pay attention to find and early treatment of benign lesions. Such as scar ulcers, pigmented nevi, especially giant nevi. Early detection and early treatment. Prognosis of the disease: skin cancer can be cured completely in early stage by surgical treatment according to the principle of plastic surgery, and the function and appearance can be preserved to the maximum extent.