Skin cancer occurs when cancer cells form in the tissues of the skin. The skin is mainly made up of two layers: the inner layer, called the dermis, and the outer layer, called the epidermis. Within the epidermis, there are three types of cells; squamous cells, basal cells, and melanocytes.  There are three types of skin cancer: basal cell carcinoma, squamous cell carcinoma, and melanoma. The types of cancer are named after the type of cells that are affected. Basal cell carcinoma and squamous cell carcinoma are very common, especially in older people. However, they are rarely lifethreatening.  Melanoma is a less common, yet more serious, type of cancer.