Melanoma, also known as malignant melanoma or malignant black, is a malignant tumor that originates from melanocytes and has a high degree of malignancy; it mostly occurs in the skin and accounts for the third place of skin malignant tumors (6.8%-20%). Malignant melanoma can evolve from congenital or acquired benign melanocytic nevus, or from malignant transformation of dysplastic nevus, or it can occur newly. The etiology of malignant melanoma has not been fully understood so far, but it is generally believed to be multifaceted. The disease is closely related to long-term sun exposure; some patients evolve from malignant freckle-like nevus, dysplastic nevus cell nevus, congenital nevus cell nevus, etc.; trauma, viral infection, and low immune function of the body may also be related to the occurrence and development of the disease. Clinical manifestations Most malignant melanomas are de novo, and during their in situ radiogenesis, the clinical manifestations are flat lesions. The important signs to identify newly developed early melanoma are the following: 1 lesion diameter of 36 mm; 2 irregular lesion margins, usually scalloped; 3 irregular and uneven pigmentation; 4 asymmetric lesions. The early manifestations of malignant melanoma are the appearance of black damage on normal skin or the recent enlargement of an existing melanocytic nevus with deepening pigmentation. With enlargement, the damage is elevated in the form of plaques or nodules, or may be myxoid or cauliflower-shaped, and the surface is easily broken and bleeding. The surface is prone to rupture and hemorrhage. The peripheral corona or halo of pigment loss is irregular. If it grows to the subcutaneous tissue, it will appear as a subcutaneous nodule or mass. If it spreads to the surrounding area, satellite damage may also appear. Malignant melanoma is classified into in situ malignant melanoma and aggressive malignant melanoma according to its mode of development, origin, disease course and prognosis. In situ malignant melanoma, also known as intraepidermal malignant melanoma, refers to malignant melanoma lesions confined to the epidermis only, in situ stage, and can be divided into three types: 1, malignant freckle-like nevus 2, superficial diffuse malignant melanoma in situ 3, invasive malignant melanoma in situ at the extremities Invasive malignant melanoma is mainly divided into four types: 1, malignant freckle-like melanoma 2, superficial diffuse malignant melanoma 3, melanoma at the extremities 4, nodal malignancy Histopathological examination of melanoma is seen in the epidermis and dermis with polydisperse or nest-like distribution of melanoma cells, expanding horizontally and vertically, reaching deep into the dermis and subcutis. Melanoma cells are heterogeneous, with varying cell size and morphology, large nuclei, and visible nucleoli, and cytoplasm containing pigment granules. Melanoma cell morphology may be diverse, with spindle-shaped and epithelioid cells predominating. Immunoperoxidase staining with anti-S-100 protein and anti-HMB-45 monoclonal antibody may be useful for diagnosis. The main factor associated with prognosis is the depth or thickness of infiltration of melanoma cells. Diagnosis and differential diagnosis This disease can be diagnosed on the basis of clinical manifestations, combined with the characteristics of the tissue case. It should be differentiated from many diseases, especially junctional nevi and mixed nevi, in addition to pigmented basal cell epithelioma, seborrheic keratosis Kaposi sarcoma, and traumatic hematoma under the nail. Treatment of malignant melanoma is more malignant, metastasis occurs more often, and the prognosis is relatively poor. Early local surgical excision is still the best way to achieve a cure, especially for early lesions. The resection methods include Mohs surgery and general surgery, and Mohs surgery should be performed to completely remove the microscopic mass. The extent of resection is 0.5-25 px next to the edge of the lesion in situ, 25 px next to the lesion if the lesion is << span="">2.0 mm thick, and 75 px next to the lesion if the lesion is >2.0 mm thick, but the extent of resection should be larger for head, neck, palm and plantar lesions, with a minimum of 37.5 px. In patients with initial diagnosis of lymph node enlargement, there should be local lymph node dissection. Patients who have metastasized can be treated with chemotherapy or combination chemotherapy, and local perfusion chemotherapy is used in the extremity malignant black section.