Pigmented nevus is a benign neoplasm composed of nevus cells, also known as nevus cell nevus, cellular nevus, melanocytic nevus, and nevus. It is common and can occur in almost everyone, from infancy to old age, and increases in number with age, often increasing significantly during pubertal development. Females tend to have more moles than males, and whites have more moles than blacks. Occasionally, they are seen on the surface of mucous membranes. There are various types of clinical manifestations: 1. Junctional nevus: Mostly seen in children and youth, rare in adults. It can occur in any part of the skin mucosa, but pigmented nevi on the palms of hands, feet and plantars, red lips and vulva are almost all junctional nevi, which can be considered as good sites. Junctional nevus has the characteristic of enlarging active nevus cells, which is called junctional vigor, and may be transformed into malignant melanoma. 2.Intradermal nevus: It is more common in middle-aged and old people, showing flat or higher than the skin surface, or warty or tipped, usually within 1cm in diameter, brown or black in color, with smooth or rough surface, and sometimes one or several hairs growing in the center. 3.Mixed nevus: Mostly seen in middle-aged and young people, it is a mildly elevated skin surface, brown to black hemispherical papule or maculopapular rash with clear boundaries, and often with hair growth. Mixed nevus should have junction vitality, so there is also the possibility of malignant transformation. 4.Halo nevus: It is named because the pigmented nevus is surrounded by a halo of pigment loss, also known as acquired teleocentric white spot. The diameter of the central pigmented nevus is about 0.5cm, and the size of the pigment loss halo varies from several millimeters to several centimeters. It is more common on the trunk, face and neck. It can be single or multiple. It is common in adolescents and has no conscious symptoms. Pathologically, it is often a mixed nevus, and can also be an intradermal nevus. 5.Spitz nevus: also known as benign juvenile nevus, spindle-shaped and epithelioid nevus, pseudomelanoma. It is an isoform of nevus, mostly mixed nevus, and can also be intradermal nevus or junctional nevus. They are pink, purplish-red, tan or black papules or nodules with clear boundaries, usually with a smooth and hairless surface, and generally <1 cm in diameter, and are found on the face and lower extremities, but also on other sites. This nevus is more common in children and is histologically similar to malignant nevus, but it is usually benign in biological behavior, so it is called benign juvenile nevus or pseudomelanoma. 6. Congenital giant nevus: It exists at birth and is characterized by a huge lesion area. Some authors advocate that a lesion area of >900 cm is the diagnostic criterion for giant nevus. Some authors believe that a lesion with an area of >2% of the body surface is considered a giant nevus. Some authors believe that the definition of giant nevus should not be based solely on the size of the area. Some lesions that occur on the neck and face, spread to the eyelids or ear drums, or occur in special areas such as hands, genitals, anus, etc., although the area is not enough for the above criteria, but if surgical excision is performed, the treatment of the trauma is more complicated, they should also be called giant nevus. Giant nevus is usually brownish to dark black, with different shades, rough surface, uneven height, and warty protrusions, and it is also called giant hairy nevus because of the thick and long hair growth. If the giant nevus is distributed on one side of the body, it is called unilateral pigmented nevus. If it occurs on the scalp and neck, it may be accompanied by molluscum melanocytosis, epilepsy and mental disorder, or even primary molluscum melanoma. Those located in the spinal region may be associated with spina bifida, cerebrospinal bulge, and other malformations. In histopathology, giant nevus is a mixed nevus or intradermal nevus. 7. Dysplastic nevus: also known as B-K nevus. It is a light brown, light red or brownish-black pigmented spot or papule with indistinct central elevation and single or multiple occurrence, with a diameter of 5 to 15 mm. It occurs on the trunk, followed by the limbs and then the face. It is more common in middle-aged and young people. Most of them are mixed nevi, and a few are junctional nevi.