Everyone has moles in one way or another, but it is not known that behind these moles there is a possibility of malignant changes. Pigmented nevus is medically called nevus cell nevus or melanocytic nevus, which is a skin manifestation caused by the increase of melanocytes in the epidermis and dermis. If it is higher than the surface of the skin, domed or papilla-like appearance or a rash with a tip, it is clinically called intradermal nevus; those slightly higher than the surface of the skin are mostly mixed nevi; those not higher than the surface of the skin are junctional nevi. The number of pigmented nevi is related to the skin color of a person, not to the intrinsic factors of the body. People with dark skin have relatively fewer nevi, and conversely, people with fair skin have more nevi. Moles usually appear between birth and before the age of 20 – 30 and vary in size and shape and color. Moles can grow everywhere on the body, but there is a kind of black child that looks very similar to moles, which is called “generalized black child” in medical science, and the black child is usually 2–8mm or larger in brown spots, mostly concentrated on the upper part of the mouth, lips, trunk and neck, but it can also occur on the face, scalp, limbs, etc. It is mostly concentrated on the upper part of the trunk and neck of the mouth and lips, but can also occur on the face, scalp, limbs and genital organs. Most of the growths are related to gastrointestinal diseases, which are difficult to determine by the naked eye and can only be determined through a series of tests. Everyone can have moles. Only when a mole changes significantly does it suggest the possibility of malignancy, and the probability of this is very low. If it increases in size in a short period of time, becomes darker, ulcerates, has blurred borders, etc., it is important to pay attention.” Junctional nevi that are subjected to friction are prone to malignant transformation Junctional nevi are a type of pigmented nevus. It can occur at any age, and mostly appears on the hands, feet, external genitalia and other parts of the body. They are prone to malignant changes because they are often subjected to friction. ”If a nevus is not in a location prone to friction, it can be ignored, but once it grows in a place prone to friction, such as the palm of the hand or the heel, it needs to be removed at a hospital as soon as possible. Junctional nevus is prone to malignant change at the location of long-term wear and tear, which should be taken seriously.” Zhang Deliang said. In addition, for some people born with hair on moles, there is no need to worry about it, but if it is hair on moles at a later stage, you need to go to the hospital to confirm the diagnosis. Some people have moles on their fingers or toes, so it is important to distinguish them clearly, “If a large mole appears in these places with many small moles next to it, the possibility of malignant change is as high as 97%. Although such cases are rare, it is better to be cautious.” Zhang Deliang said. In Yunnan, the most common symptom of nail nevus is nail black line. If it only grows on the nail, it can be ignored, but if it grows on the soft tissue of the skin, after long-term exposure to ultraviolet light or the presence of various external stimulating factors, the nail will become semi-black or completely black, and it is easy to be ignored. Its chance of malignant transformation is high, and it is easy to become malignant melanoma. Once a nevus becomes cancerous, it develops quite fast and can metastasize at an early stage. One of its metastatic pathways is through blood channels, metastasizing to lungs, liver, bones, and even brain; another pathway is through lymphatic vessels. This type of malignant melanoma is usually more malignant and difficult to treat, and there is no particularly effective treatment available. Therefore, no matter where a mole grows, if you find its irregularity, unsmoothness, abnormal color, or painful to touch, inflammation, or bleeding, you must seek medical attention immediately. After the age of 30, pigmented moles usually do not grow again, and if they are still growing it is important to distinguish whether they are moles or not. As we age, the surface of the skin that is easily exposed begins to appear somewhat rough or patchy, which is medically called “seborrheic keratosis” (commonly known as senile warts), and if neither is the case, we must seek medical attention as soon as possible. Many people choose to remove moles for aesthetic reasons, but if they are not removed thoroughly, they will not only regenerate, but even cause malignant changes. At present, there are three types of mole removal methods in the market: liquid nitrogen freezing method, laser and surgical removal. The advantage of liquid nitrogen freezing method is that it does not bleed, is not easy to produce scar, and has low cost, but it is easy to regenerate; laser is using carbon dioxide super pulse laser, which is easy to grasp the operation, the depth can be controlled, the skin trauma is small, and the recovery is fast. If malignancy is suspected, or if the nevus is particularly large, dark or deep and cannot be completely removed by non-surgical methods, it should be surgically removed, and histopathological examination can also be done to clarify the nature, but local anesthesia is needed during surgery, and scars are easily formed with surgical incisions. For conventional moles, laser removal is recommended. “Liquid nitrogen freezing, which is also commonly known as potion mole, can easily be infected and cause malignant changes, and even some intradermal moles can not be completely removed by potion alone. And laser mole removal, there are also many kinds of laser, some say laser, but in fact, it is an ion treatment instrument, which is not suitable for mole removal, it is better to use super pulse fractional laser or Q-modulated laser, otherwise, the mole will also regenerate. In addition, you should not take moles at random on the street, not only is it difficult to protect the hygiene conditions, but also it is easy to be malignant if it is not clean.” It is best to have pathological examination for surgical mole removal to confirm whether there are malignant cells; if there is no malignant change, it can be removed directly by surgery; if there are signs of malignant change, large area clearance surgery should be done or with other treatments.