Key points
- Skin cancer is a disease in which cells in the skin grow out of control.
- Too much exposure to ultraviolet (UV) rays from the sun or tanning beds causes most skin cancers.
What skin cancer is
Skin cancer is a disease in which cells in the skin grow out of control. There are different types of skin cancer. The type of skin cancer depends on which cells in the skin turn into cancer.
The skin has two main layers. The upper or outer layer is called the epidermis. The lower or inner layer is called the dermis. 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 color. When skin is exposed to the sun, melanocytes make more pigment and cause the skin to darken.
Types of skin cancer
The three most common types of skin cancer are:
- Squamous cell carcinoma, which begins in the upper (squamous) layer of the skin.
- Basal cell carcinoma, which begins in the lower (basal) layer of the skin.
- Melanoma, which begins in the melanocytes.
Basal and squamous cell carcinomas are the two most common types of skin cancer. Both can usually be cured, but treatment can leave scars.
Melanoma is the third most common type of skin cancer. Melanoma causes more deaths than other types of skin cancer because it often spreads to other parts of the body, including vital organs like the brain and liver.
Causes of skin cancer
Too much exposure to UV rays from the sun or tanning beds causes most skin cancers. UV rays can damage skin cells. In the short term, this damage can cause a sunburn. Over time, UV damage adds up, leading to changes in skin texture, early skin aging, and sometimes skin cancer.
Find out if you have a greater risk of getting skin cancer.
