Pigmented nevus, also known as nevocytic nevus or melanocytic nevus, is a benign tumor formed by the localized aggregation of nevus cells. Depending on the location of nevus cells within the skin, pigmented nevi can be classified into junctional nevi, compound nevi, and intradermal nevi. This condition is very common, affecting almost everyone, and typically follows a developmental and degenerative process. In early childhood, it appears as flat junctional nevi, which then develop into compound nevi or intradermal nevi as the individual grows, particularly during adolescence.

bubble_chart Pathological Changes

1. Junctional nevus: The localized nests of nevus cells are located at the dermo-epidermal junction.

2. Intradermal nevus: The nests of nevus cells are located within the dermis, where multinucleated nevus cells can be observed.

3. Compound nevus: The nests of nevus cells are found at the dermo-epidermal junction and the upper dermis. The dermal nevus cells are cuboidal, while the junctional nevus cells are small and contain little pigment. {|102|}

bubble_chart Clinical Manifestations

1. Junctional naevus: Mostly appears in childhood, commonly occurring on the palms, soles, nail beds, and genital areas. The lesion is flat or slightly raised, 5–6 mm in diameter, round or oval, with clearly defined borders and a brown color. The central pigmentation is darker than the periphery, the surface is smooth and hairless, and skin lines are present.

2. Intra dermal naevus: Common in adults, frequently found on the head and neck. The lesion presents as a dome-shaped or pedunculated papule or nodule, light to dark brown in color, ranging in size from a few millimeters to several centimeters, with varying amounts of hair growth on the surface.

bubble_chart Treatment Measures

Generally, no treatment is needed. Pay attention to pigmented nevi on the soles and nail beds, avoid unnecessary irritation, and refrain from applying corrosive drugs to prevent malignant transformation. If a nevus rapidly enlarges in a short period, darkens in color, develops irregular red edges, shows surface bleeding or ulceration, or exhibits satellite lesions around it, these signs indicate possible malignant transformation. In such cases, surgical excision should be performed, and the specimen should be sent for pathological examination immediately.