According to the location of nevus cells in the skin, nevus can be divided into junctional nevus, intradermal nevus and mixed nevus. Junctional nevus has nevus cells and nevus cell nests mainly between the bottom layer of epidermis and dermis, which is characterized by flat or slightly higher than the skin surface, unclear border, smooth surface, hairless, different luster, yellowish, greenish or dark color, and can be seen in any part of the body, and is more common in young people and children. Intradermal nevus, that is, nevus cells and nevus cell nests are gathered in the dermis, often flattened or higher than the skin in the shape of warts, dark brown or lacquer color, and evenly and more hairy. It is a common pigmented nevus in adults, with clear boundary and not easy to occur malignant transformation. Third, mixed nevus in which nevus cells and nevus cells nest in the deep epidermis and also in the dermis is called mixed nevus. Commonly, the center of nevus is protruding from the skin surface, with long hair, and the surrounding area is diffusely distributed, with different luster and unclear boundary, which is the component of junctional nevus, and the junctional nevus changes to intra-dermal nevus since early childhood, so the mixed nevus is rarely seen in older people. Mixed nevus and junctional nevus both have the possibility of malignant transformation. The parts of pigmented nevus that are prone to carcinogenesis: nevus in the friction area; some data show that the carcinogenesis of some pigmented nevus is related to the friction and external damage. Moles in friction-prone areas have a higher chance of becoming malignant. For example, pigmented moles growing on the palms and feet, neck, armpits, chest, head, back, genitalia and other areas susceptible to wear and tear have a high chance of malignant transformation and must be regularly observed or directly removed to prevent malignant transformation and metastasis. Secondly; moles exposed to sunlight or ultraviolet rays may increase the chance of mole changes, thus moles on long-term obviously exposed parts are best to be removed. Thirdly; moles growing on the extremities moles on the soles of the feet are good sites for melanoma, according to medical statistics, moles on the ends of the extremities, like those under the fingers or nails, should be paid special attention. Lastly; are moles that grow in mucous membranes, moles in the oral mucosa, conjunctiva, vagina and foreskin should be removed as early as possible to prevent lesions. Once again, we remind you to choose a regular hospital orthopedic department to remove moles and follow medical advice for pathological examination if necessary, and not to listen to “mole spotting” experts who roam the streets, which can be dangerous once the treatment deteriorates.