Compound nevus: common in children, most of the lesions are slightly protruding from the skin surface, and a few are papilloma-like, generally hairless, which can increase with age and become darker in color. The borderline nevus in compound nevus can be malignant. Pathological features are that intradermal nevus and residual borderline nevus often exist at the same time when nevus cells enter dermis, which is a mixed form of intradermal nevus and borderline nevus [1].

Clinically, pigmented nevus can occur at any age, mostly acquired. The disease symptoms of pigmented nevus are asymptomatic. If there are symptoms, be alert to whether it is malignant. Black, tan or blue, flat or slightly raised spots or patches; There are also a few colorless pigmented nevus. The disease is very harmful, and some pigmented nevus will become malignant and become malignant melanoma. It is reported that about 50% of malignant melanoma originated from pigmented nevus. Pigmented nevus has symptoms and changes in color and texture in a short time, so we must be vigilant and remove it as soon as possible. The following clinical changes appear, suggesting that pigmented nevus may become malignant: ① pain and itching; ② The volume increases or small "satellite nevus" appears around; 3 color changes, different shades; ④ Peripheral inflammatory flushing; ⑤ pigmented nevus has induration or ulceration. [2]

Differential diagnosis of malignant melanoma: the early stage of malignant melanoma of skin is pigmented nevus of skin. In malignant transformation, the original pigmented nevus increases rapidly, with itching, ulcer and even rupture and bleeding, and the pigment deepens, showing black or dark brown, and the edge becomes irregular, with pigment satellite nodules bleeding around the focus. Mucosal malignant melanoma is blue-black, or colorless (amelanotic malignant melanoma). The focus grows rapidly, and it is prone to ulcer, often accompanied by bleeding. [ 1]

Treatment of diseases Most pigmented nevus do not need treatment. Facial nevus can be surgically removed when it affects the appearance. When the area is large, it can be removed by stages, or it can be transferred with free skin flap or adjacent skin flap after one-time removal. If a malignant nevus is suspected, a one-time surgical resection and biopsy should be performed; The operation should make an incision on the normal skin outside the boundary of the nevus. For example, after the excision of a small mole, you can secretly peel off the wound edge of the skin and sew it directly. [ 1-3]

The prognosis of the disease is no recurrence after surgical resection.