Skin cancer is a disease in which cancerous cells form in the outer layers of the skin.
The skin has two main layers and several kinds of cells. The top layer off skin is called the epidermis. The most common skin cancers are basal cell cancer and squamous cell cancer , both of which are also called nonmelanoma skin cancers. Melanoma is a type of skin cancer that starts in the melanocytes. It is less common but more serious and difficult to treat than the other two types, so it is discussed in a separate overview.