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.

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 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.

Types

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.

Risk Factors

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.

Possible Signs

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.

Testing

Tests or procedures that examine the skin are used to detect and diagnose nonmelanoma skin cancer.

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.

Stages

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.

The following stages are used for nonmelanoma skin cancer:

• Stage 0 (Carcinoma in Situ): cancer is found only in the epidermis (topmost layer of the skin), in the layer of cells in which the cancer began. Stage 0 cancer is also called carcinoma in situ.

• Stage I: the tumor is 2 centimeters or smaller.

• Stage II: the tumor is larger than 2 centimeters.

• 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: cancer has spread to other parts of the body.

Treatment

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 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, and the patient’s general health.

There are different types of treatment for patients with nonmelanoma skin cancer and actinic keratosis.

Different types of treatment are available for patients with nonmelanoma skin cancer and actinic keratosis. Some treatments are standard (the currently used treatment), and some are being tested in clinical trials. Before starting treatment, patients may want to think about taking part in a clinical trial. A treatment clinical trial is a research study meant to help improve current treatments or obtain information on new treatments for patients with cancer. When clinical trials show that a new treatment is better than the standard treatment, the new treatment may become the standard treatment.

Clinical trials are taking place in many parts of the country. Information about ongoing clinical trials is available from the NCI Web site. Choosing the most appropriate cancer treatment is a decision that ideally involves the patient, family, and health care team.

Four types of standard treatment are used:

Surgery

One or more of the following surgical procedures may be used to treat nonmelanoma skin cancer:

• Mohs micrographic surgery: The tumor is cut from the skin in thin layers. During surgery, the edges of the tumor and each layer of tumor removed are viewed through a microscope to check for cancer cells. Layers continue to be removed until no more cancer cells are seen. This type of surgery removes as little normal tissue as possible and is often used to remove skin cancer on the face.
• Simple excision: The tumor is cut from the skin along with some of the normal skin around it.
• Shave excision: The abnormal area is shaved off the surface of the skin with a small blade.
• Electrodesiccation and curettage: The tumor is cut from the skin with a curette (a sharp, spoon-shaped tool). A needle-shaped electrode is then used to treat the area with an electric current that stops the bleeding and destroys cancer cells that remain around the edge of the wound. The process may be repeated one to three times during the surgery to remove all of the cancer.
• Cryosurgery: A treatment that uses an instrument to freeze and destroy abnormal tissue, such as carcinoma in situ. This type of treatment is also called cryotherapy.
• Laser surgery: A surgical procedure that uses a laser beam (a narrow beam of intense light) as a knife to make bloodless cuts in tissue or to remove a surface lesion such as a tumor.
• Dermabrasion: Removal of the top layer of skin using a rotating wheel or small particles to rub away skin cells.

Radiation therapy

Radiation therapy is a cancer treatment that uses high-energy x-rays or other types of radiation to kill cancer cells. There are two types of radiation therapy. External radiation therapy uses a machine outside the body to send radiation toward the cancer. Internal radiation therapy uses a radioactive substance sealed in needles, seeds, wires, or catheters that are placed directly into or near the cancer. The way the radiation therapy is given depends on the type and stage of the cancer being treated.

Chemotherapy

Chemotherapy is a cancer treatment that uses drugs to stop the growth of cancer cells, either by killing the cells or by stopping the cells from dividing. When chemotherapy is taken by mouth or injected into a vein or muscle, the drugs enter the bloodstream and can reach cancer cells throughout the body (systemic chemotherapy). When chemotherapy is placed directly into the spinal column, an organ, or a body cavity such as the abdomen, the drugs mainly affect cancer cells in those areas (regional chemotherapy). Chemotherapy for nonmelanoma skin cancer and actinic keratosis is usually topical (applied to the skin in a cream or lotion). The way the chemotherapy is given depends on the condition being treated.

Retinoids (drugs related to vitamin A) are sometimes used to treat or prevent nonmelanoma skin cancer. The retinoids may be taken by mouth or applied to the skin. The use of retinoids is being studied in clinical trials for treatment of squamous cell carcinoma.

Photodynamic therapy

Photodynamic therapy (PDT) is a cancer treatment that uses a drug and a certain type of laser light to kill cancer cells. A drug that is not active until it is exposed to light is injected into a vein. The drug collects more in cancer cells than in normal cells. Fiberoptic tubes are then used to deliver the laser light to the cancer cells, where the drug becomes active and kills the cells. Photodynamic therapy causes little damage to healthy tissue. It is used mainly to treat tumors on or just under the skin or in the lining of internal organs, such as the lungs and the esophagus.

Other types of treatment are being tested in clinical trials. These include the following:

Biologic therapy

Biologic therapy is a treatment that uses the patient’s immune system to fight cancer. Substances made by the body or made in a laboratory are used to boost, direct, or restore the body’s natural defenses against cancer. This type of cancer treatment is also called biotherapy or immunotherapy.

References

National Cancer Institute. 1 AMS Circle Bethesda, MD 20892-3675 Telephone: 1–800–4–CANCER (1–800–422–6237) TTY: 1–800–332–8615 E-Mail: cancergovstaff@mail.nih.gov. http://www.niams.nih.gov/