Causes, Risk Factors, and Prevention of Melanoma Skin Cancer

Exposure to UV rays is a major risk factor for most melanomas. Sunlight is the main source of UV rays. Tanning beds and sunlamps are also sources of UV rays.

Although UV rays make up a very small portion of the sun’s rays, they are the main cause of the damaging effects of the sun on the skin. UV rays damage the DNA (genes) inside skin cells. Skin cancers can begin when this damage affects the genes that control skin cell growth.

The pattern and timing of the UV exposure seem to play a role in melanoma development. For example:

• Melanoma on the trunk (chest and back) and legs is linked to frequent sunburns, especially in childhood. This might also have to do with the fact that these areas aren’t constantly exposed to UV light.
• Melanomas that start on the face, neck, and arms are in areas that get more constant sun exposure.

To learn more about the effects of UV rays on the skin and what you can do to protect yourself and your loved ones, see:

• Ultraviolet (UV) Radiation and Cancer Risk
• How to Protect Your Skin from UV Rays

A mole, also known as a nevus, is a benign pigmented tumor. Babies are not usually born with moles; they often begin to appear in children and young adults.

Having many moles

Most moles will never cause any problems, but someone who has many moles is more likely to develop melanoma.

Atypical moles (dysplastic nevi)

Atypical moles are often larger than other moles and have an abnormal shape or color. They can appear on skin that is exposed to the sun, as well as skin that is usually covered, such as on the buttocks or scalp.

People with atypical moles are at higher risk for melanoma, although most atypical moles never become cancer, and most melanomas seem to arise without a preexisting atypical mole.

Atypical mole syndrome (dysplastic nevus syndrome)

People with this inherited condition have many atypical moles. If at least one close relative has had melanoma, this condition is referred to as familial atypical multiple mole and melanoma (FAMMM) syndrome.

People with this condition have a very high lifetime risk of melanoma, so they need to have very thorough, regular skin exams by a dermatologist, a doctor who specializes in skin problems. Sometimes full-body photos are taken to help the doctor recognize if moles are changing or if new ones have appeared.

Many doctors recommend that people with this condition learn how to do monthly skin self-exams as well.

Moles present at birth (congenital melanocytic nevi)

People with congenital melanocytic moles have less than a 5% chance of developing a melanoma in their lifetime. The exact risk depends on the size of the mole. For example, the risk for melanoma is very low in people with congenital moles that are smaller than the palm of the hand, while those with moles that cover large portions of the back and buttocks, known as bathing trunk nevi, have a higher risk.

Congenital moles are sometimes removed by surgery so that they can’t become cancer. They might also be removed for cosmetic reasons. Whether doctors advise removing a congenital mole depends on factors such as its size, location, and color.

If they are not removed, many doctors recommend that they be examined regularly by a dermatologist and that the person be taught how to do monthly skin self-exams.

The risk of melanoma is much higher for people with lighter skin tones than for people with darker skin tones.

And among people with lighter skin, those with red or blond hair, blue or green eyes, or skin that freckles or burns easily are at higher risk.

Your risk of melanoma is higher if one or more of your first-degree relatives (parents, siblings, or children) have had melanoma. Around 1 in 10 people with melanoma have a family history of the disease.

The increased risk might be because of a shared family lifestyle of frequent sun exposure, a family tendency to have lighter skin tone, certain shared gene changes (mutations) that run in a family, or a combination of these factors.

For some people with a strong family history of melanoma, doctors might advise genetic counseling and testing to see if they have gene changes that increase their risk.

A person who has already had melanoma has a higher risk of getting melanoma again. In people who’ve had several melanomas or who’ve had melanoma at an early age, doctors might advise genetic counseling and testing to see if they have gene changes that increase their risk.

People who have had basal cell or squamous cell skin cancers are also at higher risk of melanoma.

A person’s immune system helps the body fight off cancers. People with weakened immune systems from certain diseases or medical treatments are more likely to develop many types of skin cancer, including melanoma. For example:

• People who get organ transplants are often given medicines that weaken their immune system to help prevent them from rejecting the new organ. This increases their risk of melanoma.
• People living with HIV, the virus that causes AIDS, often have weakened immune systems and are at increased risk for melanoma.
• People with certain blood cancers that can weaken the immune system, such as chronic lymphocytic leukemia (CLL) or non-Hodgkin lymphoma, have a higher risk of skin cancer, including melanoma.

The risk of melanoma increases as people age, but melanoma can also develop in younger people. In fact, melanoma is one of the most common cancers in people younger than 30, especially younger women.

Melanoma that runs in families might occur at a younger age.

In the United States, men are more likely than women to get melanoma, although this varies by age. Before age 50, the risk is higher for women. After age 50, the risk is higher in men.

XP is a rare, inherited condition that lowers skin cells’ ability to repair damage to their DNA. People with XP have a high risk of developing melanoma and other skin cancers when they are young, especially on sun-exposed areas of their skin.

The most important way to lower your risk of melanoma is to protect yourself from exposure to UV rays. Practice sun safety when you are outdoors, and avoid tanning beds.

Seek shade

Simply staying in the shade is one of the best ways to limit your UV exposure.

Use UV protection

If you are going to be in the sun:

• Wear a shirt and a wide-brimmed hat.
• Apply sunscreen to areas not covered by clothing.
• Put on sunglasses to protect your eyes and sensitive skin around them.

Avoid using tanning beds and sunlamps

Tanning lamps give off UV rays, which can cause long-term skin damage and can contribute to skin cancer. Tanning bed use has been linked with an increased risk of melanoma, especially if it is started before a person is 30 years old. Most dermatologists (skin doctors) and health organizations recommend against using tanning beds and sunlamps.

Protect children from the sun

Children need special attention, because they tend to spend more time outdoors and can burn more easily. Parents and other caregivers should protect children from excess sun exposure by using the steps above. Children need to be taught about the dangers of too much sun exposure as they become more independent.

To learn more about sun safety

For more on how to protect yourself and your family from UV exposure, see How to Protect Your Skin from UV Rays

Checking your skin regularly might help you spot any new or abnormal moles or other growths. If they appear, show them to your doctor before they have a chance to turn into skin cancer.

Certain types of moles are more likely to develop into melanoma. If you have moles, depending on how they look, your doctor might want to watch them closely with regular exams or might remove some of them for testing if they have features that suggest they might change into a melanoma.

Routine removal of many moles is not usually recommended to prevent melanoma. Some melanomas develop from moles, but most do not. If you have many moles, getting careful, routine exams by a dermatologist, along with doing monthly skin self-exams, might be recommended.

If you find a new, unusual, or changing mole, you should have it checked by a doctor. See Signs and Symptoms of Melanoma Skin Cancer for descriptions of what to look for.

Infection with HIV, the virus that causes AIDS, can weaken the immune system. Avoiding known risk factors for HIV infection, such as intravenous (IV) drug use and having unprotected sex with many partners, might lower your risk of skin cancer, as well as many other types of cancer. For more information, see HIV Infection and Cancer.