Your skin is the body’s largest organ. It helps to control body heat and stores water and fat for the body. It also protects your body from infection, injury, heat and ultraviolet (UV) radiation. There are two main layers of the skin, the epidermis or the top layer and the dermis or bottom layer. The epidermis is mostly made of flat cells called squamous cells and just below them are round cells called basal cells. Melanocytes are scattered in between the basal cells and produce pigment when the skin is exposed to ultraviolet (UV) radiation. The deeper dermis has many types of tissue such as glands, blood vessels and lymph vessels.
Skin cancer is the most common of all cancers. More than 68,000 Americans will be diagnosed with melanoma (cancer of the melanocytes) and another 48,000 will be diagnosed with an early stage of the disease that only affects the top layer of the skin. In addition, more than 2 million cases of basal cell or squamous cell skin cancer will be diagnosed in the United States every year. Melanoma is the most serious of all the skin cancers because it can spread to other parts of the body. Basal cell, squamous cell and less common forms of non-melanoma skin cancers seldom spread to other parts of the body.