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Skin Cancer Screening (PDQ®)

Patient Version

General Information About Skin Cancer

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 (top or outer layer) and the dermis (lower or inner layer). 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. Cancer that forms in squamous cells is called squamous cell carcinoma.
  • Basal cells: Round cells under the squamous cells. Cancer that forms in basal cells is called basal cell carcinoma.
  • Melanocytes: Found 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 and cause the skin to tan, or darken. Cancer that forms in melanocytes is called melanoma.
Skin anatomy; drawing shows layers of the epidermis, dermis, and subcutaneous tissue including hair shafts and follicles, oil glands, lymph vessels, nerves, fatty tissue, veins, arteries, and a sweat gland.
Anatomy of the skin, showing the epidermis, dermis, and subcutaneous tissue.

Nonmelanoma skin cancer is the most common cancer in the United States.

Basal cell carcinoma and squamous cell carcinoma are also called nonmelanoma skin cancer and are the most common forms of skin cancer. Most basal cell and squamous cell skin cancers can be cured.

Melanoma is more likely to spread to nearby tissues and other parts of the body and can be harder to cure. Melanoma is easier to cure if the tumor is found before it spreads to the dermis (inner layer of skin). Melanoma is less likely to cause death when it is found and treated early.

Anatomy of the skin with melanocytes; drawing shows normal skin anatomy, including the epidermis, dermis, hair follicles, sweat glands, hair shafts, veins, arteries, fatty tissue, nerves, lymph vessels, oil glands, and subcutaneous tissue. The pullout shows a close-up of the squamous cell and basal cell layers of the epidermis above the dermis with blood vessels. Melanin is shown in the cells. A melanocyte is shown in the layer of basal cells at the deepest part of the epidermis.
Anatomy of the skin, showing the epidermis, dermis, and subcutaneous tissue. Melanocytes are in the layer of basal cells at the deepest part of the epidermis.

In the United States, the number of cases of nonmelanoma skin cancer seems to have increased in recent years. The number of cases of melanoma has increased over the last 30 years. Part of the reason for these increases may be that people are more aware of skin cancer. They are more likely to have skin exams and biopsies and to be diagnosed with skin cancer.

Over the past 20 years, the number of deaths from melanoma has decreased slightly among white men and women younger than 50 years. During that time, the number of deaths from melanoma has increased slightly among white men older than 50 years and stayed about the same among white women older than 50 years.

See the following PDQ summaries for more information about skin cancer:

Being exposed to ultraviolet radiation may increase the risk of skin cancer.

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.

Being exposed to ultraviolet (UV) radiation and having skin that is sensitive to UV radiation are risk factors for skin cancer. UV radiation is the name for the invisible rays that are part of the energy that comes from the sun. Sunlamps and tanning beds also give off UV radiation.

Risk factors for nonmelanoma and melanoma cancers are not the same.

  • Nonmelanoma skin cancer risk factors include:
    • 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.
      • Blue or green or other light-colored eyes.
      • Red or blond hair.
    • Having actinic keratosis.
    • Past treatment with radiation.
    • Having a weakened immune system.
    • Being exposed to arsenic.
  • Melanoma skin cancer risk factors include:
    • Having a fair complexion, which includes the following:
      • Fair skin that freckles and burns easily, does not tan, or tans poorly.
      • Blue or green or other light-colored eyes.
      • Red or blond hair.
    • Being exposed to natural sunlight or artificial sunlight (such as from tanning beds) over long periods of time.
    • Having a history of many blistering sunburns, especially as a child or teenager.
    • Having several large or many small moles.
    • Having a family history of unusual moles (atypical nevus syndrome).
    • Having a family or personal history of melanoma.
    • Being white.
  • Updated: March 5, 2014