Skin cancer begins in the epidermis, which is made up of three kinds of cells:
- Squamous cells: Thin, flat cells that form the top layer of the epidermis.
- Basal cells: Round cells under the squamous cells.
- Melanocytes: Cells that make melanin and are found in the lower part of the epidermis. Melanin is the pigment that gives skin its natural color. When skin is exposed to the sun, melanocytes make more pigment and cause the skin to darken.