Skin Cancer

Skin cancer is a disease in which malignant (cancer) cells form in the tissues of the skin. It generally begins in the epidermis of the skin. There are three common types of skin cancer:

• Squamous cell carcinoma begins in squamous cells which are thin, flat cells that form the top layer of the epidermis.
• Basal cell carcinoma begins in basal cells which are round cells under the squamous cells.
• Melanoma begins in melanocytes which are 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.

Melanoma is the rarest form of skin cancer, but it is more likely to invade nearby tissues and spread to other parts of the body than nonmelanoma skin cancers. Actinic keratosis is a skin condition that sometimes develops into squamous cell carcinoma.

The following refers to nonmelanoma skin cancer and actinic keratosis. Click here for information about melanoma.

Symptoms and Diagnosis

Possible signs of nonmelanoma skin cancer include:

• 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:

• 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.

To 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.

Causes

All cancers are caused by dysfunctions of proteins involved in cell division, apoptosis, or DNA repair (see general characteristics). Dysfunctional proteins may arise from gene mutations or protein interactions with environments. Several genes are known to be associated with skin cancer (more info). The following risk factors may increase the chance of developing skin cancer:

• 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:

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

Stages

The following stages are used for nonmelanoma skin cancer:

Stage 0 (Carcinoma in Situ)

In stage 0, 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

In stage I, 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

Four types of standard treatment are used:

Surgery

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

• 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 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

Chemotherapy

Photodynamic therapy

Reference:

National Cancer Institute, USA.