Skin cancer

Skin cancer 

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 darken.

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Anatomy of the skin, showing the epidermis, dermis, and subcutaneous tissue.

Skin cancer can occur anywhere on the body, but it is most common in skin that is often 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. 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.
  • 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 male.

Risk factors for actinic keratosis 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.
  • Blue or green or other light-colored eyes.
  • Red or blond hair.

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 by apathologist 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.

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    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.

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

T

he 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.