Skin cancer is a disease in which malignant (cancer) cells form in the tissues of the skin.

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.

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.

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

• 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.

• 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.

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.

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 a pathologist 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.

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

• 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.

National Cancer Institute