Malignant melanoma is a tumor arising from melanocytes in the skin and other organs. Cutaneous melanoma presents as pigmented skin lesions that change significantly over months or years. Although its incidence is low, its malignancy is high, metastasis occurs early, and mortality is high, so early diagnosis and treatment are important. Most malignant melanomas occur in adults, and most cases of giant congenital pigmented nevi with secondary cancer are seen in children. Clinical manifestations: The clinical symptoms of cutaneous malignant melanoma include bleeding, itching, pressure pain, ulceration, etc. Generally speaking, the symptoms of melanoma are related to the age of onset. Young patients usually show itching, color change and boundary enlargement of lesions, while elderly patients usually show ulceration of lesions, which usually indicates poor prognosis. The lesion manifestations of cutaneous malignant melanoma are related to the anatomical site and the growth pattern of the tumor, i.e., to the histological type, which in turn varies greatly depending on age, type, and race. Different types of melanoma have different etiological and genetic backgrounds. The current clinical histological typing of melanoma uses the Clark typing, which includes four types: malignant freckled nevus-like melanoma (LMM); superficial diffuse melanoma; limbic freckle-like melanoma/mucosal melanoma; and nodular melanoma (NM). Among Caucasians with malignant melanoma, approximately 70% have SSM, but among all Asians with malignant melanoma, ALM occurring in less sun-exposed areas accounts for 72%. Diagnosis: The ABCDE criteria can be used for suspicious skin lesions. A (Asymmey) represents asymmetry; B (Borderirregularity) represents border irregularity; C (Colorvariegation) represents color diversification; D (Diameter>6 mm) represents diameter greater than 6 mm; E (Elevation, evolving) represents lesion elevation and progression. If the lesions meet the ABCDE criteria, malignant melanoma is highly suspected and a biopsy is needed for histopathological examination to further confirm the diagnosis. However, some subtypes, such as nodular melanoma, cannot be determined by ABCDE criteria. Histopathology: Melanocytes proliferate abnormally and form some nests within the epidermis or at the epidermal-dermal boundary. These cell nests vary in size and may fuse with each other. There are varying degrees of variability in the size and shape of the melanocytes within the nests, as well as in the shape of the nuclei. Mitosis (including abnormal mitosis) is more common than in benign pigmented nevi, and pigment granules are present in the cytoplasm of the tumor cells. In aggressive malignant melanoma, tumor cells grow infiltrating into the dermis or subcutaneous tissue. Immunohistochemical staining: tumor cells were positive for S100, HMB45 and MelanA.