Skin Cancer, an overview

Learn more about the different types of skin cancer

Skin cancer is the most common type of cancer.  The main types of skin cancer are squamous cell carcinoma, basal cell carcinoma, and melanoma. Melanoma is much less common than the other types but much more likely to invade nearby tissue and spread to other parts of the body. Most deaths from skin cancer are caused by melanoma.

  • Skin cancer is a disease in which malignant (cancer) cells form in the tissues of the skin.
  • Different types of cancer start in the skin.
  • Skin color and being exposed to sunlight can increase the risk of basal cell carcinoma and squamous cell carcinoma of the skin.
  • Basal cell carcinoma, squamous cell carcinoma of the skin, and actinic keratosis often appear as a change in the skin.
  • Tests or procedures that examine the skin are used to diagnose basal cell carcinoma and squamous cell carcinoma of the skin.
  • Certain factors affect prognosis (chance of recovery) and treatment options.

Skin cancer is the most common cancer in the United States.

Basal cell carcinoma and squamous cell carcinoma are the most common types of skin cancer in the United States. The number of new cases of nonmelanoma skin cancer appears to be increasing every year. These nonmelanoma skin cancers can usually be cured.

The number of new cases of melanoma has been increasing for at least 30 years. Melanoma is more likely to spread to nearby tissues and other parts of the body and can be harder to cure. Finding and treating melanoma skin cancer early may help prevent death from melanoma.

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

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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 three 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: Cells that make melanin and are found in the lower part of the epidermis. Melanin is the pigment that gives skin its natural color. When skin is exposed to the sun, melanocytes make more pigment and cause the skin to darken
Anatomy of the skin showing the epidermis (including the squamous cell and basal cell layers), dermis, subcutaneous tissue, and other parts of the skin.

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, and hands.

Different types of cancer start in the skin.

Skin cancer may form in basal cells or squamous cells. Basal cell carcinoma and squamous cell carcinoma are the most common types of skin cancer. They are also called nonmelanoma skin cancer. Actinic keratosis is a skin condition that sometimes becomes squamous cell carcinoma.

Melanoma is less common than basal cell carcinoma or squamous cell carcinoma. It is more likely to invade nearby tissues and spread to other parts of the body.

This summary is about basal cell carcinoma, squamous cell carcinoma of the skin, and actinic keratosis.

  • Melanoma Treatment
  • Mycosis Fungoides (Including Sézary Syndrome) Treatment
  • Kaposi Sarcoma Treatment
  • Merkel Cell Carcinoma Treatment
  • Childhood Basal Cell Carcinoma and Squamous Cell Carcinoma of the Skin Treatment
  • Genetics of Skin Cancer

Skin color and being exposed to sunlight can increase the risk of basal cell carcinoma and squamous cell carcinoma of the skin.

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. Talk with your doctor if you think you may be at risk.

Risk factors for basal cell carcinoma and squamous cell carcinoma of the skin 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, green, or other light-colored eyes.
    • Red or blond hair.Although having a fair complexion is a risk factor for skin cancer, people of all skin colors can get skin cancer.
  • Having a history of sunburns.
  • Having a personal or family history of basal cell carcinoma, squamous cell carcinoma of the skin, actinic keratosis, familial dysplastic nevus syndrome, or unusual moles.
  • Having certain changes in the genes or hereditary syndromes, such as basal cell nevus syndrome, that are linked to skin cancer.
  • Having skin inflammation that has lasted for long periods of time.
  • Having a weakened immune system.
  • Being exposed to arsenic.
  • Past treatment with radiation.

Older age is the main risk factor for most cancers. The chance of getting cancer increases as you get older.

Basal cell carcinoma, squamous cell carcinoma of the skin, and actinic keratosis often appear as a change in the skin.

Not all changes in the skin are a sign of basal cell carcinoma, squamous cell carcinoma of the skin, or actinic keratosis. Check with your doctor if you notice any changes in your skin.

Signs of basal cell carcinoma and squamous cell carcinoma of the skin include the following:

  • A sore that does not heal.
  • Areas of the skin that are:
    • Raised, smooth, shiny, and look pearly.
    • Firm and look like a scar, and may be white, yellow, or waxy.
    • Raised and red or reddish-brown.
    • Scaly, bleeding, or crusty.

Basal cell carcinoma and squamous cell carcinoma of the skin occur most often in areas of the skin exposed to the sun, such as the nose, ears, lower lip, or top of the hands.

Signs of actinic keratosis include the following:

  • A rough, red, pink, or brown, scaly patch on the skin that may be flat or raised.
  • Cracking or peeling of the lower lip that is not helped by lip balm or petroleum jelly.

Actinic keratosis occurs most commonly on the face or the top of the hands.

Tests or procedures that examine the skin are used to diagnose basal cell carcinoma and squamous cell carcinoma of the skin.

The following procedures may be used:

  • Physical exam and health history: An exam of the body to check general signs of health, including checking for signs of disease, such as lumps or anything else that seems unusual. A history of the patient’s health habits and past illnesses and treatments will also be taken.
  • Skin exam: An exam of the skin for bumps or spots that look abnormal in color, size, shape, or texture.
  • Skin biopsy: All or part of the abnormal-looking growth is cut from the skin and viewed under a microscope by a pathologist to check for signs of cancer. There are four 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.
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.
    • Incisional biopsy: A scalpel is used to remove part of a growth.
    • Excisional biopsy: A scalpel is used to remove the entire growth.

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

The prognosis for squamous cell carcinoma of the skin depends mostly on the following:

  • Stage of the cancer.
  • Whether the patient is immunosuppressed.
  • Whether the patient uses tobacco.
  • The patient’s general health.

Treatment options for basal cell carcinoma and squamous cell carcinoma of the skin depend on the following:

  • The type of cancer.
  • The stage of the cancer, for squamous cell carcinoma.
  • The size of the tumor and what part of the body it affects.
  • The patient’s general health.

There are three ways that cancer spreads in the body.

Cancer can spread through tissue, the lymph system, and the blood:

  • Tissue. The cancer spreads from where it began by growing into nearby areas.
  • Lymph system. The cancer spreads from where it began by getting into the lymph system. The cancer travels through the lymph vessels to other parts of the body.
  • Blood. The cancer spreads from where it began by getting into the blood. The cancer travels through the blood vessels to other parts of the body.

Cancer may spread from where it began to other parts of the body.

When cancer spreads to another part of the body, it is called metastasis. Cancer cells break away from where they began (the primary tumor) and travel through the lymph system or blood.

  • Lymph system. The cancer gets into the lymph system, travels through the lymph vessels, and forms a tumor (metastatic tumor) in another part of the body.
  • Blood. The cancer gets into the blood, travels through the blood vessels, and forms a tumor (metastatic tumor) in another part of the body.

The metastatic tumor is the same type of cancer as the primary tumor. For example, if skin cancer spreads to the lung, the cancer cells in the lung are actually skin cancer cells. The disease is metastatic skin cancer, not lung cancer.

Avoiding risk factors and increasing protective factors may help prevent cancer.

Avoiding cancer risk factors may help prevent certain cancers. Risk factors include smoking, being overweight, and not getting enough exercise. Increasing protective factors such as quitting smoking and exercising may also help prevent some cancers. Talk to your doctor or other health care professional about how you might lower your risk of cancer.

Being exposed to ultraviolet radiation is a risk factor for skin cancer.

Some studies suggest that being exposed to ultraviolet (UV) radiation and the sensitivity of a person’s skin to UV radiation are risk factors for skin cancer. UV radiation is the name for the invisible rays that are part of the energy that comes from the sun. Sunlamps and tanning beds also give off UV radiation.

Risk factors for nonmelanoma and melanoma cancers are not the same.

  • Risk factors for nonmelanoma skin cancer:
    • 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 exposed to arsenic.
  • Risk factors for melanoma skin cancer:
    • 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.
    • Being exposed to natural sunlight or artificial sunlight (such as from tanning beds) over long periods of time.
    • Having a history of many blistering sunburns, especially as a child or teenager.
    • Having several large or many small moles.
    • Having a family history of unusual moles (atypical nevus syndrome).
    • Having a family or personal history of melanoma.
    • Being white.

Although having a fair complexion is a risk factor for nonmelanoma and melanoma skin cancer, people of all skin colors can get skin cancer.

It is not known if the following lower the risk of nonmelanoma skin cancer:

Sunscreen use and avoiding sun exposure

It is not known if nonmelanoma skin cancer risk is decreased by staying out of the sun, using sunscreens, or wearing protective clothing when outdoors. This is because not enough studies have been done to prove this.

Sunscreen may help decrease the amount of UV radiation to the skin. One study found that wearing sunscreen can help prevent actinic keratoses, scaly patches of skin that sometimes become squamous cell carcinoma.

The harms of using sunscreen are likely to be small and include allergic reactions to skin creams and lower levels of vitamin D made in the skin because of less sun exposure.

It is also possible that when a person uses sunscreen to avoid sunburn they may spend too much time in the sun and be exposed to harmful UV radiation.

Although protecting the skin and eyes from the sun has not been proven to lower the chance of getting skin cancer, skin experts suggest the following:

  • Use sunscreen that protects against UV radiation.
  • Do not stay out in the sun for long periods of time, especially when the sun is at its strongest.
  • Wear long sleeve shirts, long pants, sun hats, and sunglasses, when outdoors.

Chemopreventive agents

Chemoprevention is the use of drugs, vitamins, or other agents to try to reduce the risk of cancer. The following chemopreventive agents have been studied to find whether they lower the risk of nonmelanoma skin cancer:

Beta carotene

Studies of beta carotene (taken as a supplement in pills) have not shown that it prevents nonmelanoma skin cancer from forming or coming back.

Isotretinoin

High doses of isotretinoin have been shown to prevent new skin cancers in patients with xeroderma pigmentosum. However, isotretinoin has not been shown to prevent nonmelanoma skin cancers from coming back in patients previously treated for nonmelanoma skin cancers. Treatment with isotretinoin can cause serious side effects.

Selenium

Studies have shown that selenium (taken in brewer’s yeast tablets) does not lower the risk of basal cell carcinoma, and may increase the risk of squamous cell carcinoma.

Celecoxib

A study of celecoxib in patients with actinic keratosis and a history of nonmelanoma skin cancer found those who took celecoxib had slightly lower rates of recurrent nonmelanoma skin cancers. Celecoxib may have serious side effects on the heart and blood vessels.

Alpha-difluoromethylornithine (DFMO)

A study of alpha-difluoromethylornithine (DFMO) in patients with a history of nonmelanoma skin cancer showed that those who took DFMO had lower rates of nonmelanoma skin cancers coming back than those who took a placebo. DFMO may cause hearing loss which is usually temporary.

Nicotinamide (vitamin B3)

Studies have shown that nicotinamide (vitamin B3) helps prevent new actinic keratoses lesions from forming in people who had four or fewer actinic lesions before taking nicotinamide. More studies are needed to find out if nicotinamide prevents nonmelanoma skin cancer from forming or coming back.

It is not known if the following lower the risk of melanoma:

Sunscreen

It has not been proven that using sunscreen to prevent sunburn can protect against melanoma caused by UV radiation. Other risk factors such as having skin that burns easily, having a large number of benign moles, or having atypical nevi may also play a role in whether melanoma forms.

Expanded information on the different types of skin cancer

Medika has reproduced the following NCI sourced information for your convenience. We recommend visiting the NCI for any additional information and resources. Open the appropriate NCI page by clicking on listed source below the article.

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