Melanoma is mostly seen in adults over 30 years of age and occurs in the skin, mucous membranes and internal organs. The prognosis of most melanomas is poor, and lymphatic and blood metastases can occur in advanced stages. It is a tumor arising from melanocytes of 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 early treatment are important. Most malignant melanomas occur in adults, and cases of giant congenital pigmented nevi with secondary cancer are mostly seen in children. Causes of melanoma 1. Frequent stimulation of pigmented nevi There is a correlation between melanoma and nevi, and 60% of malignant melanoma is derived from the malignant transformation of pigmented nevi. Most of the malignant melanoma occurs due to the malignant transformation of the black pigmented nevus caused by repeated rubbing, grasping up and injury, and inappropriate digging and drug erosion can transform the benign black pigmented nevus into malignant melanoma. 2.Related to endocrine The rapid development of malignant melanoma in women during pregnancy or childbearing age suggests that this disease is related to endocrine. 3. Prevalent in benign nevi 84% of malignant melanoma comes from benign nevi. Because the moles are so small, many patients do not notice them at the beginning of the disease. It is believed that benign moles are the biggest source of malignant melanoma. 4.Atmospheric pollution The massive emission of harmful substances such as Freon destroys the ozone layer, resulting in inadequate ultraviolet filtration, and harmful ultraviolet rays and harmful substances in the air work together on human skin, causing abnormal expression of melanocytes and triggering melanoma. Many people use a lot of chemical cosmetics in order to pursue clean and tender skin, resulting in chemical skin pollution, and some people even use chemical corrosives to remove moles on the skin, which is counterproductive and stimulates the excessive proliferation of melanocytes. 6.Lack of health knowledge The nevus that grows on the foot, perineum and other parts that are easy to be rubbed does not attract enough attention, and is squeezed and rubbed for a long time, which eventually leads to its malignant transformation. 7.Abuse of estrogen drugs There are estrogen receptors in the cells of malignant melanoma, so it is suspected that excessive estrogen will stimulate the occurrence of melanoma. 8.Immunodeficiency With the improvement of living standard, Chinese people live significantly longer. Along with ageing, the immune function of the body gradually declines. Low immune function is one of the important reasons for the occurrence of melanoma, so the incidence of melanoma in the elderly is clinically high. 9.Benign melanotic plaques, i.e. nevi, of which junctional nevi are most likely to become malignant, mixed nevi are less likely to become malignant, and endothelial nevi are rarely malignant. However, most of the scalp melanomas are not transformed from nevi, so some people think that this disease is not completely related to nevi.