If in the friction parts, such as male beard, neck, waist, armpits, groin, hands and feet, etc., the long-term friction and stimulation of these places of pigmented moles can indeed be malignant, early treatment is correct; the wrong aspect lies in the method of treatment, in the early years, there are patients because of pigmented nevus impede the face of the laser cauterization – that is, “point off” did not point clean and stimulate the proliferation of melanocytes instead of malignant changes reported. “Point off” not point clean and stimulate melanocyte proliferation but the report of malignant changes, although the chance of this is very low, but the regular medical institutions generally do not choose laser “point”, liquid nitrogen freezing or drug corrosion method, the preferred method of treatment is surgery The preferred treatment is surgery, which is a clean excision that will not recur and will not cause malignant changes. Nevus pigmentosus, also known as nevus cell nevus, is the most common benign skin tumor in human beings, which can exist at birth, but often occurs after 2 years of age, without conscious symptoms. Depending on the location of the nevus in the skin, they are usually categorized as junctional nevus, mixed nevus and intradermal nevus. Generally there is no need for treatment. Congenital nevi have the possibility of developing melanoma, so surgical excision is generally preferred. Junctional nevus and mixed nevus occurring in the friction area should also be considered for surgical excision. For acquired nevus, if there are signs of malignant transformation: sudden increase in size, black color, surface erosion and ulceration, conscious pain and itching, satellite foci around the nevus, etc., surgical excision should be performed immediately. Recently, there are pigmented nevus, seborrheic keratosis, subnail bruise, pyogenic granuloma and basal cell carcinoma among these patients, but no case of malignant melanoma has been found yet. Malignant melanoma, referred to as malignant black or melanoma, is a malignant tumor originating from melanocytes, which mostly occurs in the skin, and can also be seen in the choroid of the eye and the soft meninges. Its development is related to sunlight exposure, racial heredity, malignant transformation of benign pigmented nevi, traumatic stimulation, viral infection, immune function and many other aspects. According to the clinical manifestations, they are divided into superficial diffuse melanoma, nodular melanoma, limb freckle nevus-like melanoma and malignant freckle nevus-like melanoma. The degree of malignancy of acral naevus-like melanoma is the highest, because not all types of melanoma have high mortality rate, and the prognosis of in situ melanoma and invasive melanoma in pathological classification is very different, so the public should not talk about “tumors” when they are on the alert.