Nevi are benign skin swellings formed by nest-like arrangement of melanocytes, which originate from neurospinal cells in the ectoderm and are distributed in the basal layer of the skin, hair follicles, mucous membranes, etc. Nevi are divided into congenital nevi and acquired nevi in terms of age of onset. Congenital nevus is a nevus that appears at birth or within 6 months after birth. All types of congenital nevi have the possibility of malignant transformation. Only junctional nevi and the junctional component of compound nevi have the possibility of malignant transformation. In clinical work, it is found that nevi are roughly divided into is which stage, the first stage nevus, divided into mixed nevus, intradermal nevus, junctional nevus. The second stage, benign melanoma. The third stage malignant melanoma. The incidence of nevus is rising, and the rise of benign melanoma is more obvious. Malignant melanoma is a highly malignant tumor that occurs mostly in adults and is rare in children. Malignant melanoma in children accounts for 1 to 4 percent of all melanomas and 3 percent of childhood tumors. The incidence has been on the rise in recent years. The most common primary sites are extremities, areas prone to friction (including palms, soles, finger (toe) ends, under the nail, etc.). The etiology of childhood melanoma is not yet clear, and it is believed that both environmental and genetic factors are involved. Environmental factors, such as prolonged exposure to ultraviolet radiation, etc., and some scholars believe that whether a child’s melanoma becomes malignant or not is closely related to the size of the nevus, and congenital giant nevus should be alerted to the possibility of malignant transformation. Clinical features suggesting malignant transformation of nevi are rapid enlargement, rupture, bleeding, satellite foci in the periphery, and formation of palpable nodule-like bumps. Surgical excision is still the main treatment for nevus in children. In 1991, the WHO Melanoma Study Group pointed out that there was no recurrence of lesions less than 1 mm thick, regardless of the surgical margin, and there was a difference in recurrence rate between patients with a thickness of 1-2 mm and a margin of 25 px and 75 px, but no difference in survival. Cryotherapy is an option for physical therapy. Melanoma cells are destroyed by freezing at about -7°, while the slowing of local blood supply and blockage of microcirculation caused by freezing further leads to cellular ischemia and hypoxia or even death, which to some extent both kills the tumor cells and blocks their metastasis to distant sites. Superficial melanocytes For children with lymph node metastasis or distant metastasis, postoperative adjuvant radiotherapy, chemotherapy, and biologically targeted therapy should be used. There is no uniform standard and relevant information is still lacking.