Malignant melanoma is a tumor arising from melanocytes in the skin and other organs. Primary melanomas are caused by the proliferation of melanocytes in the epidermis and appear as heavily pigmented, progressively enlarged nodules surrounded by a red halo. Although its incidence is lower than that of basal cell carcinoma and squamous cell carcinoma, its malignancy is large, metastasis occurs early and mortality rate is high. Reasons affecting melanin formation 1, extracellular factors In recent years, the molecular biology of melanin formation has proved that the activity of melanocytes to produce melanin is controlled by the network. Melanocytes, keratinocytes, Langerhans cells, fibroblasts, vascular endothelial cells, nerve cells, etc. in the skin form a “telecommunications” interactive network (i.e. cytoplasmic network). In this network, many cytokines have an impact on the reproduction and differentiation of melanocytes, dendrite formation and melanin synthesis. Factors that promote melanocyte growth and survival include: basic fibrillogenic growth factor (bFGF), endothelin (ET-1), nerve cell growth factor (NGF), etc.; factors that inhibit melanocyte proliferation and reduce tyrosinase activity include: interleukin I (aIL-la), interleukin-6, tumor necrosis factor (SCF), etc. promote melanocyte differentiation and melanin synthesis; interferon (IFN) can cause melanocyte morphological changes and growth inhibition under certain conditions; inflammatory mediator leukotriene CA (LTC4) is a pro-dividing source of human melanocytes, which can cause rapid proliferation of melanocytes and has a chemotactic effect on melanocytes. 2, intracellular influencing factors (1) the view of multi-enzyme action. The rate of melanin synthesis in melanocytes is determined by a variety of intracellular enzymes. For many years, it has been believed that tyrosinase is the only enzyme required in the process of melanin biosynthesis. As research on melanin synthesis continues to progress, it has been discovered that other substances associated with melanin synthesis are present in melanocytes. Two tyrosinase-related proteins, TPRl (DHIcA oxidase) and TRP2 (dopachrome intercalase), play an important role in melanin synthesis. In addition to their assisting role in the synthesis of melanin by tyrosinase, they also have an important role in the synthesis of other different types of pigments. (2) Melanocyte-regulated signaling pathways. Many cytokines, such as basic fibrillogenic growth factor, hepatocyte growth factor/diffusion factor, and endothelin, promote melanocyte proliferation in vitro, and some of them stimulate tyrosinase activity and make melanocytes highly pigmented. These factors may enter the cell through the receptors on the melanocyte membrane surface and regulate the corresponding targets by downstream signaling, causing cellular material mainly protein phosphorylation or dephosphorylation, and exerting regulatory effects on melanocyte proliferation and differentiation. 3, the impact of exogenous factors Ultraviolet light is a long-term exposure of the human body to an external stimulus, is the main physiological stimulus for human melanocyte proliferation and increased skin pigmentation. Skin darkening is mainly caused by medium and long-wave ultraviolet radiation (UVB and UVA), which can cause the proliferation of melanocytes and promote melanin production, skin pigmentation.