Skin Cancer

General Information | Treatment Options | Screening | Prevention

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General Information
  • About
  • Risk Factors
  • Signs & Symptoms
  • Detection
  • Stages

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

  • Melanoma Treatment
  • Mycosis Fungoides and the Sézary Syndrome Treatment
  • Kaposi Sarcoma Treatment
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 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.

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 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.
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.

Stages of Skin Cancer

After nonmelanoma skin cancer has been diagnosed, tests are done to find out if cancer cells have spread within the skin or to other parts of the body.

The process used to find out if cancer has spread within the skin or to other parts of the body is called staging. The information gathered from the staging process determines the stage of the disease. It is important to know the stage in order to plan treatment. A biopsy is often the only test needed to determine the stage of nonmelanoma skin cancer. Lymph nodes may be examined in cases of squamous cell carcinoma to see if cancer has spread to them.

There are three ways that cancer spreads in the body.

The three ways that cancer spreads in the body are:

  • Through tissue. Cancer invades the surrounding normal tissue.
  • Through the lymph system. Cancer invades the lymph system and travels through the lymph vessels to other places in the body.
  • Through the blood. Cancer invades the veins and capillaries and travels through the blood to other places in the body.

When cancer cells break away from the primary (original) tumor and travel through the lymph or blood to other places in the body, another (secondary) tumor may form. This process is called metastasis. The secondary (metastatic) tumor is the same type of cancer as the primary tumor. For example, if breast cancer spreads to the bones, the cancer cells in the bones are actually breast cancer cells. The disease is metastatic breast cancer, not bone cancer.

The following stages are used for nonmelanoma skin cancer:Stage 0 (Carcinoma in Situ)

In stage 0, abnormal cells are found in the squamous cell or basal cell layer of the epidermis (topmost layer of the skin). These abnormal cells may become cancer and spread into nearby normal tissue. Stage 0 is also called carcinoma in situ.

Stage I

In stage I, cancer has formed and the tumor is 2 centimeters or smaller.

Stage II

In stage II, the tumor is larger than 2 centimeters.

Stage III

In stage III, cancer has spread below the skin to cartilage, muscle, or bone and/or to nearby lymph nodes, but not to other parts of the body.

Stage IV

In stage IV, cancer has spread to other parts of the body.

Treatment choices are based on the type of nonmelanoma skin cancer or precancerous skin condition diagnosed:Basal cell carcinoma

Basal cell carcinoma is the most common type of skin cancer. It usually occurs on areas of the skin that have been in the sun, most often the nose. Often this cancer appears as a small raised bump that has a smooth, pearly appearance. Another type looks like a scar and is flat and firm to the touch. Basal cell carcinoma may spread to tissues around the cancer, but it usually does not spread to other parts of the body.

Squamous cell carcinoma

Squamous cell carcinoma occurs on areas of the skin that have been in the sun, such as the ears, lower lip, and the back of the hands. Squamous cell carcinoma may also appear on areas of the skin that have been burned or exposed to chemicals or radiation. Often this cancer appears as a firm red bump. Sometimes the tumor may feel scaly or bleed or develop a crust. Squamous cell tumors may spread to nearby lymph nodes.

Actinic keratosis

Actinic keratosis is a skin condition that is not cancer, but sometimes changes into squamous cell carcinoma. It usually occurs in areas that have been exposed to the sun, such as the face, the back of the hands, and the lower lip. It appears as rough, red, pink, or brown, raised, scaly patches on the skin, or cracking or peeling of the lower lip that is not helped by lip balm or petroleum jelly.

Cancer information from the NCI PDQ service