Nonmelanoma is the most common type of skin cancer and can usually be treated successfully. Melanoma (malignant melanoma) is more serious and can be deadly. There are two types of nonmelanoma skin cancer: basal cell carcinoma, which is slow growing, and squamous cell carcinoma, which grows more quickly. Actinic keratosis is a precancerous skin lesion. Skin cancer often starts in a mole, and skin cancer signs include changes in moles. Skin cancer prevention involves protection from the sun starting in infancy. Treatment includes Mohs surgery and mole removal.