While it’s true that sun exposure plays a starring role in many cases of melanoma, there may be other factors that determine why one person develops melanoma and another a harmless mole. What are the triggers and which among them do we have any control over? We take a look at the causes of melanoma and what you can do to ward off this skin cancer.
We asked the nation’s top experts in melanoma for the most up-to-date information possible:
Ellen Marmur, M.D.Associate Clinical Professor in the Departments of Dermatology and Genomics and Genetic Science
Mary L. Stevenson, M.D.Assistant Professor of Dermatology
Philip Friedlander, M.D.Assistant Professor of Hematology and Oncology
What Is Melanoma Exactly?
Melanoma is a type of skin cancer that happens when pigment-making cells (known as melanocytes) get damaged and start growing out of control, forming a tiny cancerous tumor in the skin. Whether you have the fairest of skin or the deepest, dark complexion, we all have melanocytes, doing their thing without any of us paying much notice.
Ultraviolet light (UV)—a form of radiation from the sun’s rays—along with genetics, underlying conditions, and other factors can trigger changes in the DNA of these cells, which can lead to melanoma. While it’s primarily a skin disease, melanoma can occasionally pop up in other places melanocytes are found, including eyes (known as ocular melanoma) or inside mucous linings like genitals (known as mucosal melanoma).
1. Melanocytes’ (very important) function is to pump out melanin, a pigment that is supposed to help absorb UV light so it doesn’t reach (and damage) skin cells that are deeper down in the dermis.
2. Dark skin types are not immune to UV damage. They just have some natural sun protection, because their cells produce more melanin. Dark complexions don’t have more melanocytes than fair skin does; the cells are just more active. In fair skin, the melanin tends to come out spotty in the form of freckles.
3. UV rays often find a way to penetrate skin. When they do, they may cause damage in the DNA of your skin cells.
4. If one of the affected cells is a melanocyte, the damaged cell can turn into melanoma. How? Healthy cells grow and divide new cells, and old and damaged cells die off. But the more damaged a cell becomes, it starts doing its own thing—rapidly growing and dividing into more and more damaged cells until it forms a malignant tumor
5. A melanoma doesn’t always present as a funny-looking mole that has you calling your dermatologist. Sometimes, it looks like a harmless mole or spot that only a doctor would recognize as dangerous.
What Is the Main Cause of Melanoma?
Experts believe that UV exposure causes most cases of melanoma. In fact, 86% of all melanomas stem from it, according to a study in the British Journal of Cancer. But exactly how much sun is enough to do damage?
Melanoma is typically associated with intense bursts of sun — the type of sun exposure that leaves you with a red, angry sunburn. In fact, having just five sunburns over your lifetime doubles your risk for melanoma, and one single blistering burn as a child more than doubles the chance of developing melanoma as an adult.
This is why fair skin types are more vulnerable to melanoma. Paler types tend to redden after even a short amount of time in the sun, but having a complexion that tans easily doesn’t mean you’re safe from skin cancer either. That’s because having more melanin on your skin’s surface doesn’t necessarily protect your skin cells from UV damage.
UV light doesn’t just come from the sun, but from tanning beds too. The UV light produced in these beds can also damage melanocytes and spur melanoma growth. Tanning beds can be even more dangerous than natural sunlight, emitting three times the amount of UVA rays (rays that penetrate deeply into the skin versus UVB rays, which affect skin’s surface) than the sun. Plus, it’s a likely bet that anyone frequenting a tanning bed isn’t wearing sunscreen. Women who used a tanning bed for the first time before age 35 increased their risk for melanoma by 75% compared to those who never used a tanning bed, according to research in the International Journal of Cancer.
While sun causes the majority of melanomas, that’s not the only story. Some types of melanomas show up where the sun doesn’t shine. For example, acral lentiginous melanoma, more common in African Americans, pops up on the bottoms of feet and between toes. There are also melanomas that form in mucosal liningsinside your body, including in the gastrointestinal tract. Last time we checked, the GI tract can’t get sunburned, so what gives? Genetics.
Can Melanoma Be Genetic?
Family history plays a big role in melanoma. One in 10 melanoma patients have (or had) a family member with this type of skin cancer, and if it’s a first-degree relative (a parent, sibling, or child), there’s a greater risk. Compared with those without a family history of melanoma, those with a family history of melanoma had a 74% increased risk of melanoma, according to a recent study in the Journal of the American Academy of Dermatology.
If you have a family member with melanoma along with many—over 50—moles, some of which are atypical (unusual-looking moles that may have irregular characteristics when looked at under a microscope), you may have familial atypical multiple mole melanoma syndrome, a condition that makes you more prone to developing melanomas.
A few inherited genetic mutations can also make you more prone to melanoma. If you have a strong family history of melanoma, you may want to ask your dermatologist about genetic testing. Knowing you carry one of the genes below doesn’t guarantee you’ll wind up with melanoma, but it can make you more careful about sun exposure and staying on top of routine skin checks.
CDKN2A: This is the most common gene mutation linked to melanoma. People who carry the mutation on this gene are at greater risk for melanoma as they age. One study in the Journal of the National Cancer Institute showed the risk for developing melanoma is 14% by age 50, but jumps to 28% by age 80. People who carry this gene are also a greater risk for developing pancreatic cancer.
CDK4: This gene mutation is associated with atypical moles and familial melanoma.
BAP1: This one puts you at risk for melanoma of the skin and eyes, mesothelioma (a cancer of the tissue lining the lungs, stomach, heart, and other organs), along with kidney cancer.
MC1R: It’s the so-called redhead gene because people who carry variants of this gene have higher levels of pheomelanin, a type of melanin that gives lips and nipples a pinkish color. High amounts of pheomelanin creates ginger hair color, fair skin, and freckles. This gene variant doubles one’s risk of melanoma, according to a study published in JAMA Dermatology.
BRCA 1 or 2: The research on this one is mixed, but some studies have found that these gene mutations—known for their connection to breast and ovarian cancer—also bring a slightly increased risk of melanoma, as well as pancreatic cancer.
What Are Other Known Risk Factors For Melanoma?
Researchers have identified a few other things that could increase chances of getting melanoma:
The gender you were born with seems to play a role, but that may have more to do with lifestyle habits than hormones or anatomy. Males are more likely to develop melanoma than women, and they’re also more likely to die from it. By age 65, men are twice as likely as women to get melanoma, according to the American Academy of Dermatology. Why? Experts still aren’t sure, but they suspect it’s because men are less likely to wear sunscreen and go for regular skin checks. Not only are they developing melanomas from UV rays, they’re being diagnosed at later stages.
As mentioned, fair skin types are more likely to get melanoma. But that’s not to say those with darker skin tones can’t; Hispanics, Asians, and African Americans do get melanomas. These melanomas are harder to detect and tend to pop up in areas that don’t get sun exposure (like nails and soles of the feet), and the survival rates for African Americans with melanoma is less than it is for other ethnicities. The five-year survival rate for Africans Americans with melanoma is 65% versus 91% for whites, research has shown.
It’s typically been thought of as an older person’s disease and, indeed, the average age of a person diagnosed with melanoma is 65—but plenty of young people are getting it too. According to the Melanoma Research Alliance, melanoma is the most diagnosed cancer for 25- to 29-year-olds.
If you’ve had melanomas in the past, or even other types of skin cancers such as basal cell or squamous cell carcinoma, you’re at higher risk for melanoma. A study in JAMA Dermatology showed that 60% of people who’ve had one skin cancer will have another in the next 10 years.
Dealing with one of the conditions below makes you more vulnerable to melanoma.
Immune Compromised: If your immune system, the body’s personal defense system, is weakened, you’re more vulnerable to bacteria, viruses, and even cancer such as melanoma. A weakened immune system can be the result of a certain condition or medication. For instance, an autoimmune condition such as Lupus, in which your immune system attacks itself, can leave you defenseless against other threats. Diseases such as heart disease, diabetes, and AIDS lower immune function,as do medications, including chemotherapy, corticosteroids, and anti-rejection drugs. Organ transplant patients are twice as likely to develop melanoma as the general population, and researchers point to the immune-suppressing anti-rejection meds they take following a transplant.
Xeroderma pigmentosum (XP), an inherited condition that impairs your DNA’s ability to repair itself, can put you at risk for all skin cancers, including melanoma.
In the case of ocular melanoma, which occurs inside the eye, sun exposure is a biggie. But having light eyes, being older, or having pigmented spots or moles on the eye or eyelid can also increase the risk for developing this type of melanoma.
Can Melanoma Be Prevented?
Now that we know what causes melanoma, and that it's nearly always treatable when caught early, how do we avoid getting it in the first place? While certain factors are out of your control (gender and genes, for example), sun protection is one thing you can focus on. Here’s how:
Avoid the sun during peak hours: The sun’s rays are the strongest between 10 AM and 4 PM, so try not to bask during this time period.
Wear sun protective clothing: Look for ultraviolet protection factor (UPF) clothing. These tightly woven garments effectively shield skin from sun’s rays;at the beach or pool, wide-brimmed hats and rash guards are musts.
Sunscreen: Don’t leave home without it. SPF 30 should be the minimum you use on both face and body and look for one that says broad spectrum. That means it shields skin from both UVA and UVB rays — both are linked to skin cancers. Apply it to exposed areas on even cloudy, winter days; (UVA rays penetrate through clouds year-round).
Avoid the tanning salon: It’s estimated that more than 10,000 cases of melanoma in the United States, Europe, and Australia can be linked to tanning beds. Tanning while under age 35 is linked to a 75% increase in developing melanoma, research has shown. Whatever your age, just don’t.
Wear sunglasses: The best way to protect eyes from ocular melanoma is to shield them from UV light. Look for a label that says “100% protection against UVA and UVB rays.” Not all sunglasses do this.
What About Skin Checks?
Beyond sun protection, regular skin checks are your first defense. By catching it early, you can prevent cancer from spreading to other parts of the body, which is when melanoma becomes most deadly. In melanoma’s earliest form—when it is only present on the top layer of skin—the five-year survival rate is 98%.
Most people should have their skin checked by a dermatologist at least once a year. If you’ve had another type of skin cancer, plan to see your derm every six months for at least a few years (you’ll likely be able to stretch out those skin checks over time). And if you’ve already had melanoma, in-office skin checks should be done every three months for the first few years. But don’t just leave it to the pros: Know your own skin and moles and look for any changes once a month.
What exactly are you looking for? What experts call the ABCDEs of melanoma.
A is for asymmetry. If you fold the mole in half, does it match up perfectly? If not, it’s asymmetrical.
B is border. If the edges of your mole are jagged, not smooth, it’s a red flag.
C is for color. Melanomas are typically dark brown or black with uneven pigment within the mole. But they can also be red, blue-ish, and clear (known as amelanotic melanoma).
D is for diameter. You’re looking for moles as big as a pencil eraser (about ¼-inch). The majority of early melanomas grow this big, but don’t dismiss smaller specs with the other characteristics.
E is for evolving. Suspicious moles are ones that are changing in size, color, or texture.
If you discover something suspicious during a skin check, don’t panic. Make an appointment with a board-certified dermatologist, who can take a closer look and perform a biopsy if necessary.
Frequently Asked QuestionsMelanoma Causes and Prevention
How common is melanoma?
Sadly, the numbers keep growing. Melanoma is the second most-common cancer for men ages 20 to 39 (testicular cancer holds the number-one spot) and the third for women in the same age bracket, behind lymphoma and breast cancer, respectively. Melanoma is far more common in Caucasians—they’re 27-times more likely to develop the cancer than Hispanics and African Americans.
Is melanoma more likely to form in an existing mole?
No, research has shown that the majority of melanomas pop up as new spots. Seventy percent of melanomas are new growths, while close to 30% come from an existing mole.
Is an atypical mole cancerous?
No, but it can turn into cancer and if you have more than 10 of them, the risk of developing melanoma is 12 times greater than someone without atypical moles. An atypical mole is one that looks unusual—it stands out from the rest. It also looks highly irregular under a microscope. A dermatopathologist will grade atypical moles as mild, moderate, or severely atypical. Severely atypical moles (and sometimes even moderate ones) are often removed with a margin of skin since they’re at an even higher risk for turning cancerous down the road.
What are the stages of melanoma?
There’s a lot that goes into staging, including tumor thickness, whether it’s ulcerated (with broken skin similar to a wound), and where it has spread to. And within each stage, there are multiple sub-stages. In simplest terms, stage 0 is melanoma in situ, when the tumor is contained to the top layer of skin. With Stage I, the tumor is no more than 2 mm and hasn’t spread anywhere beyond the skin. In Stage II, the tumor can be anywhere from 1 mm to over 4 mm, but it hasn’t spread to lymph nodes. In stage III, the tumor has spread to nearby lymph nodes, or areas of the skin near the primary tumor, also known as satellite tumors. With Stage IV, your tumor can be any thickness and has spread to distant lymph nodes and other organs, most commonly the brain, liver, bones, or lungs.
Tanning Beds and Melanoma Risk:International Journal of Cancer. (2007). “The Association of Use of Sunbeds with Cutaneous Malignant Melanoma and Other Skin Cancers: A Systematic Review.” ncbi.nlm.nih.gov/pubmed/17131335
Family History and Melanoma Risk:Journal of the American Academy of Dermatology. (2019). “Having a First-Degree Relative with Melanoma Increases Lifetime Risk of Melanoma, Squamous Cell Carcinoma, and Basal Cell Carcinoma.” ncbi.nlm.nih.gov/pubmed/31230976
CDKN2A and Melanoma Risk:Journal of the National Cancer Institute. (2005). “Lifetime Risk of Melanoma in CDKN2A Mutation Carriers in a Population-Based Sample.” ncbi.nlm.nih.gov/pubmed/16234564
Diabetes and Melanoma:Iran Journal of Public Health. (2014). “Type 2 Diabetes Mellitus and Risk of Malignant Melanoma: A Systematic Review and Meta-Analysis of Cohort Studies.” ncbi.nlm.nih.gov/pmc/articles/PMC4401051/