Skin cancer refers to malignant proliferative lesions of the skin and its associated surrounding tissues, etc. Because there are more skin tissues that are cancerous, the manifestations of different types vary slightly. Skin cancer is a general term for malignant skin tumors, but there are many different types of actual skin cancer, such as basal cell carcinoma and malignant melanoma, as well as squamous cell carcinoma. The more common types are squamous and basal cell carcinomas. Basal cell carcinoma may have no obvious symptoms in the early stage, but after it develops, a hard papule will grow on the skin surface, partly raised like a wart, mostly in exposed areas such as the face and around the nose. When the papules rupture, ulcers will occur, with irregular shape and raised edges, and patients often have no painful and itchy symptoms, which are easily ignored. Before developing squamous cell carcinoma, patients may have precancerous lesions such as leukoplakia vulgaris or heliokeratosis, which can easily turn into skin cancer after deterioration. This type of skin cancer will have cauliflower-like or butterfly-like ulcers on the surface of the skin, and when co-infection occurs, the affected area will ooze pus, smell bad and feel painful. Malignant melanoma is easier to detect because the cancerous area is mostly black. If you find black spots suddenly appearing on various parts of the body, hands and feet, etc., and they grow rapidly within a short period of time, and the skin there is prone to rupture and ulceration, you should be careful of malignant melanoma. In summary, there are various types of skin cancer depending on the location and nature of the cancer. Commonly, basal cell carcinoma will grow papules and rupture easily, while squamous cell carcinoma will have epidermal ulcers, pus and bad odor after infection.