In dermatology clinics, patients often ask: “I have several moles on my body, is it dangerous and should I have surgery to cut them off? In fact, moles are medically classified as skin tumors, and most moles are benign tumors that grow on the skin. Why is a mole a tumor? From the medical point of view, moles are nests or clusters formed by mole cells proliferating in the skin. Because nevus cells can secrete melanin particles, the surface of the nevus appears black or brown, hence the name nevus or pigmented nevus. It is estimated that each person has about 20 pigmented nevi on average, which can be seen on any person and any part of the body, with the most common ones on the face, neck and back. They are most common on the face, neck, and back. Some are innate, while others are acquired and appear after 2 years of age. Most of the moles grow slowly or last for many years without any changes or uncomfortable symptoms. With age, nevus cells gradually move from the superficial layer of the skin into the dermis, and their number gradually increases, usually peaking at puberty. Moles are divided into three types according to where they are deposited in the skin: moles with cells distributed in the dermis are called intradermal moles, which appear as papilloma-like bumps, and almost all hemispherical and tipped moles are intradermal moles, which are stable and the safest; moles with cells distributed between the dermis and epidermis are called junctional moles, most of which are flat and have the greatest risk of becoming malignant tumors, and are therefore the most dangerous. Most of them are flat and have the greatest risk of turning into malignant tumors and are therefore the most dangerous: moles that have both of these properties are called mixed moles, which are slightly higher than the skin and have a certain tendency of malignant transformation. Most people do not care about “moles” and only try to remove those moles that are detrimental to beauty. In fact, the biggest danger of moles is cancer, so moles with the following characteristics should be removed as soon as possible: moles that grow on easily rubbed areas may have a higher chance of becoming malignant; sunlight or ultraviolet rays may increase the chances of moles changing, so moles that grow on obviously exposed areas should be removed; moles on the soles of the feet are a good site for melanoma. Medical statistics show that many moles at the end of the limbs are prone to malignant changes, such as moles under the fingers or fingernails, so special attention should be paid to them. There are two kinds of treatment methods for moles, surgical and non-surgical. Surgical treatment is suitable for nevus with larger area or malignant signs, and pathological examination should be done to determine the degree of benign and malignant nevus and to understand the condition of the surgical cut edge. Non-surgical treatments, such as laser, electrocautery, freezing, chemical cautery, etc., are only suitable for moles with a diameter of less than 5 mm, superficial, clear diagnosis and long-term stability. The choice of method for mole removal should follow the doctor’s opinion. Repeated photothermal and other effects may increase the chance of malignant changes in moles and must be used with caution. Some patients with pigmented nevi that show no obvious signs of malignancy may be followed up for a long time. If the changes described in the previous section occur, prompt consultation and early treatment are required.