There are two categories of skin cancer: melanomas and non-melanomas. Melanoma is a dangerous cancer that develops in skin pigment cells called melanocytes, which are responsible for your skin color. A melanoma looks like a dark, misshapen mole, and it's likely to develop on an existing mole. Non-melanomas can develop on any area of the body that receives a lot of direct sunlight, like the face, arms or neck, and appear in the form of lesions and tumors. Almost all skin cancers are non-melanomas.