What is skin cancer? Skin cancer, i.e. malignant tumor of the skin, is named differently according to the origin of tumor cells, including epidermis, skin appendages, skin soft tissue, peripheral nerves, melanocytes, skin lymphatic reticular tissue and hematopoietic tissue. There are also some metastatic tumors that occur in other tissues that metastasize to the skin. The common classifications include basal cell carcinoma, squamous cell carcinoma, malignant melanoma, etc., which account for about 90% of skin cancer. Basal cell carcinoma is a hard patchy papule at the beginning, some of them are raised in the shape of warts, and then break down into ulcer foci, irregular, with raised edges and uneven bases, growing slowly, mostly occurring singly, mostly on the cheeks, nose and sides of the nose, the tumor is not painful or itchy, and there is often no conscious discomfort. It first develops as a shallow ulcer with translucent nodular elevation, and then gradually expands to invade surrounding tissues and organs, becoming an invasive ulcer. Based on its morphology and pathological changes, basal cell carcinoma can be classified into four types, namely nodular ulcerative type, pigmented type, hard scarred or fibrotic type, and superficial type. Squamous cell carcinoma can be transformed from keratosis, mucosal leukoplakia and other precancerous diseases. It grows rapidly and forms ulcers at an early stage. Some of them are nodular, papillary or cauliflower-shaped, with small invasion to the deeper part and movable base, while some are butterfly-shaped, with more obvious infiltration to the deeper part and large destructive, often involving bones. Squamous cell carcinoma co-infection has mucous pus with foul smell and pain. The malignancy of squamous cell carcinoma is higher, and it is more likely to metastasize, mostly regional lymph node metastasis.