Topic updated: June 2012

Melanoma

Skin cancer is the most common type of cancer in the United States. Each year, more than 68,000 Americans are diagnosed with melanoma, and another 48,000 are diagnosed with an early form of the disease that involves only the top layer of skin. Also, more than 2 million people are treated for basal cell or squamous cell skin cancer each year. Basal cell skin cancer is several times more common than squamous cell skin cancer.

The Skin

Your skin protects your body from heat, injury, and infection. It also protects your body from damage caused by ultraviolet (UV) radiation (such as from the sun or sunlamps).

Your skin stores water and fat. It helps control body heat. Also, your skin makes vitamin D.

The skin has two main layers: the outer epidermis and the inner dermis.

  • Epidermis: The epidermis is the top layer of your skin. It’s mostly made of flat cells called squamous cells.

    Below the squamous cells deeper in the epidermis are round cells called basal cells.

    Cells called melanocytes are scattered among the basal cells. They are in the deepest part of the epidermis. Melanocytes make the pigment (color) found in skin. When skin is exposed to UV radiation, melanocytes make more pigment, causing the skin to darken, or tan.

  • Dermis: The dermis is the layer under the epidermis. The dermis contains many types of cells and structures, such as blood vessels, lymph vessels, and glands. Some of these glands make sweat, which helps cool your body. Other glands make sebum. Sebum is an oily substance that helps keep your skin from drying out. Sweat and sebum reach the surface of your skin through tiny openings called pores.

Understanding Cancer

Normal cells grow and divide to form new cells as the body needs them. When normal cells grow old or get damaged, they usually die, and new cells take their place.

But sometimes this process goes wrong. New cells form when the body doesn’t need them, and old or damaged cells don’t die as they should. The buildup of extra cells often forms a mass of tissue called a growth or tumor.

Growths on the skin can be benign (not cancer) or malignant (cancer). Benign growths are not as harmful as malignant growths.

Benign growths (such as moles)

  • Are rarely a threat to life
  • Generally can be removed and usually don’t grow back
  • Don’t invade the tissues around them
  • Don’t spread to other parts of the body

Malignant growths (such as melanoma, basal cell cancer, or squamous cell cancer)

  • May be a threat to life
  • Often can be removed but sometimes grow back
  • May invade and damage nearby organs and tissues
  • May spread to other parts of the body

Melanoma

  • Melanoma begins in melanocytes (pigment cells). Most melanocytes are in the skin.

    Melanoma can occur on any skin surface. In men, it’s often found on the skin on the head, on the neck, or between the shoulders and the hips. In women, it’s often found on the skin on the lower legs or between the shoulders and the hips.

    Melanoma is rare in people with dark skin. When it does develop in people with dark skin, it’s usually found under the fingernails, under the toenails, on the palms of the hands, or on the soles of the feet.

 

Who’s at Risk?

When you’re told that you have skin cancer, it’s natural to wonder what may have caused the disease. The main risk factor for skin cancer is exposure to sunlight (UV radiation), but there are also other risk factors. A risk factor is something that may increase the chance of getting a disease.

People with certain risk factors are more likely than others to develop skin cancer. Some risk factors vary for the different types of skin cancer.

Risks for Any Type of Skin Cancer

Studies have shown that the following are risk factors for the three most common types of skin cancer:

  • Sunlight: Sunlight is a source of UV radiation. It’s the most important risk factor for any type of skin cancer. The sun’s rays cause skin damage that can lead to cancer.
  • Severe, blistering sunburns: People who have had at least one severe, blistering sunburn are at increased risk of skin cancer. Although people who burn easily are more likely to have had sunburns as a child, sunburns during adulthood also increase the risk of skin cancer.

    • Lifetime sun exposure: The total amount of sun exposure over a lifetime is a risk factor for skin cancer.

    • Tanning: Although a tan slightly lowers the risk of sunburn, even people who tan well without sunburning have a higher risk of skin cancer because of more lifetime sun exposure.
    • Sunlight can be reflected by sand, water, snow, ice, and pavement. The sun’s rays can get through clouds, windshields, windows, and light clothing.

      In the United States, skin cancer is more common where the sun is strong. For example, more people in Texas than Minnesota get skin cancer. Also, the sun is stronger at higher elevations, such as in the mountains.

      Doctors encourage people to limit their exposure to sunlight.
  • Sunlamps and tanning booths: Artificial sources of UV radiation, such as sunlamps and tanning booths, can cause skin damage and skin cancer.  Health care providers strongly encourage people, especially young people, to avoid using sunlamps and tanning booths. The risk of skin cancer is greatly increased by using sunlamps and tanning booths before age 30.

  • Personal history: People who have had melanoma have an increased risk of developing other melanomas. Also, people who have had basal cell or squamous cell skin cancer have an increased risk of developing another skin cancer of any type.

  • Family history: Melanoma sometimes runs in families. Having two or more close relatives (mother, father, sister, brother, or child) who have had this disease is a risk factor for developing melanoma. Other types of skin cancer also sometimes run in families. Rarely, members of a family will have an inherited disorder, such as xeroderma pigmentosum or nevoid basal cell carcinoma syndrome, that makes the skin more sensitive to the sun and increases the risk of skin cancer.

  • Skin that burns easily: Having fair (pale) skin that burns in the sun easily, blue or gray eyes, red or blond hair, or many freckles increases the risk of skin cancer.

  • Certain medical conditions or medicines: Medical conditions or medicines (such as some antibiotics, hormones, or antidepressants) that make your skin more sensitive to the sun increase the risk of skin cancer. Also, medical conditions or medicines that suppress the immune system increase the risk of skin cancer.

Other Risk Factors for Melanoma

The following risk factors increase the risk of melanoma:

  • Dysplastic nevus: A dysplastic nevus is a type of mole that looks different from a common mole. A dysplastic nevus may be bigger than a common mole, and its color, surface, and border may be different. It’s usually wider than a pea and may be longer than a peanut. A dysplastic nevus can have a mixture of several colors, from pink to dark brown. Usually, it’s flat with a smooth, slightly scaly or pebbly surface, and it has an irregular edge that may fade into the surrounding skin.

    A dysplastic nevus is more likely than a common mole to turn into cancer. However, most do not change into melanoma. A doctor will remove a dysplastic nevus if it looks like it might have changed into melanoma.

  • More than 50 common moles: Usually, a common mole is smaller than a pea, has an even color (pink, tan, or brown), and is round or oval with a smooth surface. Having many common moles increases the risk of developing melanoma.

Read the rest of this great article from the National Cancer Institute.

woman in garden wearing a sunhat

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