Malignant melanoma is a kind of skin tumor with high malignancy, mostly occurs in the skin surface, accounting for 7%~20% of skin malignant tumors, and its incidence rate accounts for 1%~3% of all malignant tumors in foreign countries. The incidence rate of malignant melanoma in white race is the highest, the incidence rate of 100 people in Queensland, Australia is as high as 28.4/100,000, the incidence rate of malignant melanoma in China is about 0.8/100,000. In recent years, the incidence of cutaneous malignant melanoma is rapidly increasing in many countries, and the corresponding mortality rate is also increasing, and the age of onset is getting earlier and earlier, so people pay attention to it. Cutaneous malignant melanoma is a malignant tumor that originates from normal melanocytes or nevus cells in the epidermis and occurs mainly in middle and old age. There is no significant difference in the incidence of malignant melanoma between men and women. The overall distribution of incidence sites: head and neck, trunk and lower extremities each account for about 25%, upper extremities (including subxiphoid malignant melanoma) account for about 12.5%, and other sites account for 12.5%, but the distribution of sites varies greatly by gender, with men accounting for about 50% of malignant melanoma occurring in the trunk and women accounting for about 50% of malignant melanoma occurring in the extremities, especially in the lower extremities. Among blacks, more than 60% of malignant melanomas occur in the lower extremities, and half of the patients have lesions on the soles of the feet. The causative factors of malignant melanoma are: a. ultraviolet radiation; b. racial genetic factors; c. malignant transformation of existing pigmented nevi; d. endocrine factors; e. trauma and chronic irritation factors; f. immune factors.