A melanocytic nevus is what we usually call a nevus. Most of them occur in children or adolescence, but they can also be present at birth, progress slowly and have no conscious symptoms. Most of them are yellow, brown or black in color, but there are also blue, purple or colorless nevi, which are benign neoplasms composed of nevus cells. According to the location of nevus cells in the skin, they can be divided into 3 categories: 1. Junctional nevus: they are present at birth or occur after birth, with a diameter of 0.1-1 cm, smooth and hairless surface, flat or above the skin surface, brown, brown or black, and can occur on any part of the body. If it occurs in palmoplantar or scrotum, it is mostly a junctional nevus. 2.Mixed nevus: Mostly seen in children or teenagers. It is slightly higher than junctional nevus. 3.Intradermal nevus: Mostly seen in adults, with hemispherical elevation, papilloma-like or tipped, brown, black or colorless, and may have hair. Tip: Any intradermal nevus with hair is benign and usually does not become malignant. Most people have moles, but the probability of cancer is very small. Intersecting nevi have a higher chance of malignancy. Intersecting nevi and mixed nevi occurring in the palmoplantar, under the nail, between the waist, armpit, groin, genitalia, shoulder, mucous membrane and other friction-prone areas are often at risk of transforming into malignant melanoma because of repeated over-stimulation and should be removed. Signs of malignancy, such as sudden increase in size, irregular border, darkening, surface erosion, exudation, crusting, bleeding, ulceration, inflammatory swelling, spontaneous pain or itching, and satellite lesions around it must be immediately sought for medical treatment to exclude the possibility of malignant melanoma and should be completely removed early. It is entirely possible to cure malignant melanoma early through treatment because malignant melanoma grows at the intraepidermal level in the early stage and basically does not metastasize as long as it is treated through extended excision and adjuvant therapy. If treatment is abandoned early, it will slowly enter the vertical growth phase, invade into the dermis, and cause metastasis through blood vessels and lymphatic vessels.