Skin cancer is a disease in which malignant (cancer) cells form in
the tissues of the skin.
The skin is the body’s largest organ. It protects against heat,
sunlight, injury, and infection. Skin also helps control body temperature and stores water, fat, and vitamin D. The skin has several layers, but the two main layers are the epidermis (upper or outer layer) and the dermis (lower or inner layer). Skin cancer begins in the epidermis, which is made up of 3 kinds of cells:
Squamous cells: Thin, flat cells that form the top layer of the epidermis.
in the lower part of the epidermis, these cells make melanin, the pigment
that gives skin its natural color. When skin is exposed to the sun, melanocytes
make more pigment, causing the skin to darken.
Anatomy of the skin, showing the epidermis, dermis, and subcutaneous tissue.
This summary refers to the treatment of nonmelanoma skin cancer and actinic keratosis. Nonmelanoma skin cancers rarely spread to other parts of the body. Melanoma, the rarest form of skin cancer, is more likely to invade nearby tissues and spread to other parts of the body. See the following PDQ summaries for information on melanoma and other kinds of skin cancer:
Skin color and exposure to sunlight can affect the risk of developing nonmelanoma skin cancer and actinic keratosis.
Anything that increases your chance of getting a disease is called a risk factor. Having a risk factor does not mean that you will get cancer; not having risk factors doesn’t mean that you will not get cancer. People who think they may be at risk should discuss this with their doctor. Risk factors for basal cell carcinoma and squamous cell carcinoma include the following:
Being exposed to natural sunlight or artificial sunlight (such as from tanning beds) over long periods of time.
Having a fair complexion, which includes the following:
Fair skin that freckles and burns easily, does not tan, or tans poorly.
Punch biopsy: A special instrument called a punch or a trephine is used to remove a circle of tissue from the abnormal-looking growth.
Punch biopsy. A hollow, circular scalpel is used to cut into a lesion on the skin. The instrument is turned clockwise and counterclockwise to cut down about 4 millimeters (mm) to the layer of fatty tissue below the dermis. A small sample of tissue is removed to be checked under a microscope. Skin thickness is different on different parts of the body.