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 (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.
• Basal cells: Round cells under the squamous cells.
• 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, causing the skin to tan, or darken.

Skin cancer can occur anywhere on the body, but it is most common in skin that has been exposed to sunlight, such as the face, neck, hands, and arms. There are several types of cancer that start in the skin. The most common types are basal cell carcinoma and squamous cell carcinoma, which are nonmelanoma skin cancers. Actinic keratosis is a skin condition that sometimes develops into squamous cell carcinoma.

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. Refer to the following PDQ summaries for information on melanoma and other kinds of skin cancer:

• Melanoma Treatment
• Mycosis Fungoides and the Sézary Syndrome Treatment
• Kaposi's Sarcoma Treatment

Skin color and exposure to sunlight can affect the risk of developing nonmelanoma skin cancer and actinic keratosis.

Risk factors for basal cell carcinoma and squamous cell carcinoma include the following:

• Being exposed to a lot of natural or artificial sunlight.
• Having a fair complexion (blond or red hair, fair skin, green or blue eyes, history offreckling).
• Having scars or burns on the skin.
• Being exposed to arsenic.
• Having chronic skin inflammation or skin ulcers.
• Being treated with radiation.
• Taking immunosuppressive drugs (for example, after an organ transplant).
• Having actinic keratosis.

Risk factors for actinic keratosis include the following:

• Being exposed to a lot of sunlight.
• Having a fair complexion (blond or red hair, fair skin, green or blue eyes, history of freckling).

Nonmelanoma skin cancer and actinic keratosis often appear as a change in the skin.

Not all changes in the skin are a sign of nonmelanoma skin cancer or actinic keratosis, but a doctor should be consulted if changes in the skin are seen.

Possible signs of nonmelanoma skin cancer include the following:

• A sore that does not heal.
• Areas of the skin that are:
  • Small, raised, smooth, shiny, and waxy.
  • Small, raised, and red or reddish-brown.
  • Flat, rough, red or brown, and scaly.
  • Scaly, bleeding, or crusty.
  • Similar to a scar and firm.

Possible signs of actinic keratosis include the following:

• A rough, red, pink, or brown, raised, scaly patch on the skin.
• Cracking or peeling of the lower lip that is not helped by lip balm or petroleum jelly.

Tests or procedures that examine the skin are used to detect (find) and diagnose nonmelanoma skin cancer and actinic keratosis.

The following procedures may be used:

• Skin examination: A doctor or nurse checks the skin for bumps or spots that look abnormal in color, size, shape, or texture.
• Biopsy: All or part of the abnormal-looking growth is cut from the skin and viewed under a microscope to see if cancer cells are present. There are 3 main types of skin biopsies:
  • Shave biopsy: A sterile razor blade is used to "shave off" the abnormal-looking growth.
  • Punch biopsy: A special instrument called a punch or a trephine is used to remove a circle of tissue from the abnormal-looking growth.
  • Excisional biopsy: A scalpel is used to remove the entire growth.

Certain factors affect prognosis (chance of recovery) and treatment options.

The prognosis (chance of recovery) depends mostly on the stage of the cancer and the type of treatment used to remove the cancer.

Treatment options depend on the following:

• The stage of the cancer (whether it has spread deeper into the skin or to other places in the body).
• The type of cancer.
• The size and location of the tumor.
• The patient's general health

Health Professional Version

Nonmelanoma skin cancer

Evidence suggests that reduction of exposure to ultraviolet (UV) radiation will reduce the incidence of nonmelanoma skin cancer. Sun exposure can be reduced by changing patterns of outdoor activities to reduce time of exposure to high-intensity UV radiation, and by using adequate amounts of sufficiently protective sunscreens or wearing protective clothing when exposed to sunlight.[1]

Levels of Evidence

1b: Evidence obtained from at least one well-designed and conducted randomized controlled trial with a generally accepted intermediate endpoint.

3aii: Evidence obtained from well-designed and conducted cohort or case-control analytic studies, preferably from more than one center or research group, with a cancer incidence endpoint.

5: Opinions of respected authorities based on clinical experience or reports of expert committees.

Cutaneous melanoma

Evidence suggests that avoidance of sunburns, especially in childhood and adolescence, may reduce the incidence of cutaneous melanoma. Sunburn can be avoided by changing patterns of outdoor activities to reduce time of exposure to high-intensity UV radiation, by wearing protective clothing when exposed to sunlight, and by using adequate amounts of sufficiently protective sunscreen. Sunscreen is not a substitute for avoidance of sun exposure.[1,2]

Levels of Evidence

3aii: Evidence obtained from well-designed and conducted cohort or case-control analytic studies, preferably from more than one center or research group, with a cancer incidence endpoint.

4aii: Ecologic (descriptive) studies with a cancer incidence endpoint.

5: Opinions of respected authorities based on clinical experience or reports of expert committees.

The National Cancer Institute (NCI) is a component of the National Institutes of Health (NIH), one of eight agencies that compose the Public Health Service (PHS) in the Department of Health and Human Services (DHHS). The NCI, established under the National Cancer Act of 1937, is the Federal Government's principal agency for cancer research and training.