Pigmented nevus, nevus cell nevus is probably not known to many people, but its common name is estimated to be a household name, that is “nevus”, after watching “Do Not Disturb 2” it is estimated that many people want to get rid of it, so let’s take a look at the knowledge about pigmented nevus. Pigmented nevus, also known as nevus cell nevus, nevus, commonly known as “nevus”, is a benign new organism caused by the accumulation of nevus cells into nests. This disease can occur from infancy to old age, and almost everyone has it, with an obvious increase in adolescence. It is a developmental abnormality in which localized accumulation of melanocytes is caused by an accidental abnormality during the movement of melanocytes from the neural crest to the epidermis during development. The basic damage of pigmented nevus is mostly circular or oval-shaped patches, papules or nodules with clear borders and uniform color, generally less than 6mm in diameter, and may be brown, blue-black, black or normal skin color, etc. According to the distribution of nevus cells, they are divided into junctional nevus, intradermal nevus and mixed nevus. 1.Junctional nevus: nevus cells nest at the junction of true epidermis, light brown to dark brown rash, smooth and not protruding, present at birth or appearing soon after birth. 2.Mixed nevus: also known as compound nevus, nevus cells nest at the junction of true epidermis and dermis, brown or black macules slightly protruding from the skin, mostly seen in children and teenagers. 3.Intradermal nevus: nevus cells nest in the dermis, often appearing as hemispherical raised papules or nodules, mostly seen in adults. Pigmented nevus does not remain unchanged, but needs to go through the growth process from maturity to aging, that is, from junctional nevus to mixed nevus and finally to intradermal nevus. Pigmented nevi usually do not require treatment. Early treatment is needed when pigmentation appears as follows: 1. local pain, burning, stinging and itching often occur; 2. satellite foci appear at the edges; 3. sudden enlargement, color deepening or color becoming uneven; 4. when breakage or bleeding occurs. Especially pigmented nevi occurring in the palmoplantar, groin, armpit and other friction-prone areas need to be closely observed. Removal of pigmented nevus generally advocates surgical excision, and treatments such as laser, drug application or freezing are not recommended because nests of nevus cells may be very deep, and these treatments cannot remove nevus cells in deeper locations, but tend to stimulate nevus cells.