Melanoma Causes and Risk Factors: What Increases Your Risk

Key Takeaways

• Melanoma develops when UVA and UVB radiation (from the sun or tanning beds) damage DNA in melanocytes, the pigment-producing cells of the skin.

• UV exposure is the primary modifiable cause, but melanoma can develop in areas with no sun exposure at all, driven by genetic or other factors.

• Tanning beds are classified by the International Agency for Research on Cancer (IARC) as a Group 1 carcinogen: the same category as tobacco, and first use before age 35 increases melanoma risk by approximately 75%.

• Having 50 or more common moles, or any atypical mole (dysplastic nevus), significantly raises your lifetime risk.

• Genetics matter: a first-degree relative with melanoma approximately doubles your risk; mutations in the CDKN2A gene carry a lifetime risk approaching 70% in some studies.

• Melanoma affects people of all skin tones, the risk is lower in people with darker skin but is not zero, and the sites where it most commonly appears differ.

What Causes Melanoma?

Melanoma arises from melanocytes, the cells in the skin responsible for producing melanin pigment. When the DNA in these cells is damaged, most often by ultraviolet radiation from the sun or tanning beds, abnormal cell growth and division can lead to a malignant tumor. In addition to UV radiation, genetic predisposition, the number and type of moles on the skin, immune system status, and personal history all contribute to individual risk. In some cases, particularly in acral and mucosal melanoma, UV exposure is not the primary driver at all.

UV Radiation and Sun Exposure

UVA and UVB radiation are both implicated in melanoma development, though through somewhat different mechanisms.

UVB radiation is primarily absorbed in the outer layers of the skin. It causes direct DNA damage by creating thymine dimers, abnormal chemical bonds between adjacent thymine bases in the DNA strand. These mutations, if not repaired, can initiate the cascade that leads to cancer. UVB intensity varies with time of day, season, altitude, and latitude, and it is the primary driver of sunburn.

UVA radiation penetrates more deeply into the skin and operates throughout the day with less variation by season. It damages DNA indirectly, primarily through the generation of reactive oxygen species (free radicals). UVA also degrades collagen and is the dominant factor in photoaging. It passes through glass and clouds. Both UVA and UVB contribute to melanoma risk.

Cumulative lifetime exposure matters. Years of regular sun exposure, even without burning, accumulate DNA damage over time. This is reflected in the increased melanoma incidence with age and the particular risk associated with outdoor occupations and life in high-UV geographies.

Childhood sunburns are especially significant. Multiple blistering sunburns in childhood and adolescence substantially increase lifetime melanoma risk. The skin is more vulnerable to UV damage during development, and the mutations caused by early burns can remain dormant for decades.

Intermittent intense exposure: the pattern typical of people who work primarily indoors but have high UV exposure during vacations or weekend recreation, is associated with a higher relative risk of melanoma than continuous moderate exposure. This pattern of sporadic intense sun exposure appears to be more disruptive to melanocytes than steady chronic exposure.

Geographic and altitude factors. UV intensity increases at higher altitudes and at latitudes closer to the equator. People who live or spend significant time at high altitude or in high-UV regions have proportionally higher melanoma rates.

Tanning Beds and Artificial UV

Tanning beds are not a safe alternative to sun exposure. The World Health Organization’s International Agency for Research on Cancer (IARC) classifies ultraviolet radiation-emitting tanning devices as a Group 1 carcinogen: the highest classification, indicating sufficient evidence of cancer causation in humans.

The risk is particularly acute for young users. First use of a tanning bed before age 35 has been associated with an approximately 75% increase in the risk of developing melanoma. Risk increases with frequency of use and cumulative session time. The UV doses delivered by some commercial tanning beds exceed those of midday summer sun.

Despite widespread awareness campaigns, tanning bed use remains common in young women, the demographic where melanoma rates have been rising. If you have used tanning beds in the past, your risk is elevated, and more frequent skin monitoring and dermatology appointments are warranted. Avoiding further artificial UV exposure remains important regardless of prior use.

Genetics and Family History

Genetics plays a meaningful role in melanoma risk. Having a first-degree relative (parent, sibling, or child) with melanoma approximately doubles your personal risk. This reflects both shared genetic variants and shared environmental exposures (such as similar sun habits and fair skin in family members).

A small percentage of melanoma cases, estimated at 5–10%, are associated with identifiable high-penetrance genetic mutations:

CDKN2A (cyclin-dependent kinase inhibitor 2A) is the most commonly implicated high-risk gene. Mutations in CDKN2A impair the normal regulation of cell division. Lifetime melanoma risk in carriers ranges widely by study and family history but can approach 70% in high-risk families in regions with high UV exposure. CDKN2A mutations are associated with Familial Atypical Multiple Mole and Melanoma (FAMMM) syndrome.

CDK4 mutations are rare but also confer substantially elevated risk by disrupting a different component of cell cycle regulation.

FAMMM syndrome (Familial Atypical Multiple Mole and Melanoma) is characterized by multiple atypical moles, a personal or family history of melanoma, and in many cases, identifiable mutations in CDKN2A or CDK4. Individuals with FAMMM syndrome require intensive surveillance and may benefit from genetic counseling.

Lower-penetrance variants in genes such as MC1R (the “red hair gene”), MITF, and others also contribute to population-level melanoma risk, though the absolute risk increase from any single low-penetrance variant is smaller.

If you have two or more close relatives with melanoma, multiple primary melanomas yourself, or melanoma in combination with pancreatic cancer in your family, genetic counseling is worth pursuing. Identifying a mutation does not change the cancer that has already occurred, but it informs surveillance intensity for you and the option of cascade testing for family members.

Moles: A Major Risk Marker

The number and character of moles on your skin is one of the most useful risk markers for melanoma.

Total mole count. Having 50 or more common benign moles (nevi) is associated with a significantly elevated melanoma risk compared to having fewer. Having 100 or more moles raises the risk further. This doesn’t mean any one mole is likely to turn cancerous, the vast majority of moles never do, but a higher total number means more cells that could potentially undergo malignant transformation.

Atypical moles (dysplastic nevi). A dysplastic nevus is a mole with irregular features, asymmetrical shape, uneven color, ill-defined borders, that does not fully meet the criteria for melanoma but is histologically abnormal. Having even one atypical mole is a stronger risk marker than having many typical moles. Having multiple atypical moles, or atypical moles with a family history of melanoma, substantially elevates risk and is associated with FAMMM syndrome.

Giant congenital nevi. A congenital nevus is a mole present at birth. Giant congenital nevi (generally defined as those reaching 20 cm or more in diameter in adulthood) carry a lifetime risk of malignant transformation estimated at 2–10%. Smaller congenital nevi carry much lower risk but may still warrant monitoring.

It is important to emphasize: the overwhelming majority of moles, even atypical ones, never become melanoma. A higher mole count means more careful monitoring, not inevitable disease. Most people with 50 or more moles, and most people with atypical moles, never develop melanoma. What is called for is awareness, regular self-exam, and routine dermatology care, not anxiety.

Other Risk Factors

Several additional factors influence melanoma risk:

Fair skin, light eyes, and light hair. Melanin provides partial protection against UV radiation. People with naturally fair skin, light-colored eyes (blue, green, or gray), and red or blond hair have less melanin and thus less protection, and higher melanoma risk. People who freckle or burn rather than tan are at elevated risk.

Personal history of melanoma. Having had one melanoma substantially increases the risk of developing a second primary melanoma. Lifelong surveillance is essential.

Personal history of other skin cancers. A history of basal cell carcinoma or squamous cell carcinoma also indicates significant cumulative UV damage and correlates with elevated melanoma risk.

Immune suppression. Immunosuppression: whether from an organ transplant (requiring anti-rejection medications), HIV/AIDS, or certain autoimmune therapies, impairs the immune system’s ability to identify and destroy early malignant cells. People with immunosuppression have significantly elevated rates of all skin cancers, including melanoma.

Prior radiation therapy. Radiation to a field of skin (for example, for lymphoma or other cancers) can increase long-term skin cancer risk in that area.

Xeroderma pigmentosum. This rare inherited condition impairs the body’s ability to repair UV-induced DNA damage, leading to an extremely high rate of skin cancers including melanoma, often beginning in childhood.

Does Melanoma Only Affect Fair-Skinned People?

No, and this is one of the most important misconceptions to correct.

Melanoma is significantly more common in people with lighter skin tones, and the absolute risk for any given person of color is lower than for a fair-skinned person with equivalent sun exposure. However, melanoma does occur in people of all skin tones, and the consequences of the misconception that darker skin confers complete protection can be severe.

In people with darker skin, melanoma most often presents as acral lentiginous melanoma: a subtype that arises on the palms, soles, and under the nails, where UV exposure is not the primary driver. This subtype is more commonly diagnosed in Black, Asian, and Hispanic individuals and is not well captured by standard sun-protection messaging. Because acral sites are often overlooked in skin self-exam and clinical exams, and because the assumption of near-zero risk can delay evaluation of a suspicious lesion, people with darker skin tones are more often diagnosed at a later, less treatable stage, contributing to worse outcomes.

Bob Marley, for example, was diagnosed with acral lentiginous melanoma under his toenail and died of the disease at 36. His diagnosis illustrates precisely why the “melanoma only affects fair-skinned people” assumption is not just inaccurate but potentially dangerous.

If you have darker skin, you are not at zero risk. Examine your palms, soles, and nails regularly. Any new dark streak under a nail, irregular patch on the palm or sole, or unusual spot anywhere on the body warrants evaluation, regardless of skin tone.

For more on recognizing melanoma across skin tones, see melanoma symptoms and melanoma screening. For subtype-specific information, see types of melanoma. For information on getting checked, see melanoma diagnosis.

If you’ve been diagnosed with melanoma, clinical trials offer access to treatments that weren’t available even a few years ago. Search current trials through North’s trial finder.

Frequently Asked Questions

What is the main cause of melanoma?

The primary cause of most melanomas is ultraviolet (UV) radiation from the sun or tanning beds. UV radiation, both UVA and UVB, damages the DNA in melanocytes (skin pigment cells), and if that damage is not repaired, it can trigger abnormal cell growth. Cumulative lifetime UV exposure, intermittent intense exposure, and childhood sunburns all contribute. However, melanoma can also develop in areas with minimal sun exposure, such as the palms, soles, and under the nails, where genetic factors and other biological drivers are more relevant.

Do tanning beds cause melanoma?

Yes. The International Agency for Research on Cancer classifies UV-emitting tanning devices as a Group 1 carcinogen: the highest level of evidence, the same category as tobacco. First use of a tanning bed before age 35 increases the risk of melanoma by approximately 75%, and risk increases further with frequency and total exposure time. There is no safe level of tanning bed use. The UV doses emitted by commercial tanning beds are intense and directly damage melanocyte DNA.

Is melanoma genetic?

Genetics play a meaningful role in melanoma risk. Having a first-degree relative with melanoma approximately doubles your risk. Specific high-penetrance mutations, most commonly in the CDKN2A gene, are found in a subset of melanoma families and can confer a lifetime risk approaching 70% in high-risk settings. Lower-penetrance variants in genes like MC1R also contribute to population-level risk. If you have multiple affected relatives or multiple personal primary melanomas, genetic counseling is worth discussing with your oncologist.

Can you get melanoma without sun exposure?

Yes. While UV radiation is the primary driver of most cutaneous melanomas, some subtypes, particularly acral lentiginous melanoma and mucosal melanoma, occur on sites with little or no sun exposure and are driven by different biological mechanisms. Melanoma can also develop in the eye (ocular melanoma), the mouth, the vagina, the anus, and other mucosal surfaces where UV is not a relevant factor. This is why melanoma screening and self-examination should cover the entire body, not just sun-exposed areas.

What moles are most likely to become melanoma?

Atypical moles (dysplastic nevi), those with irregular shape, uneven color, and ill-defined borders, carry a higher individual risk of malignant transformation than typical moles, and their presence is associated with elevated overall melanoma risk. Giant congenital nevus (present at birth, 20 cm or more in diameter) carry an estimated 2–10% lifetime transformation risk. Having 50 or more ordinary moles also elevates risk statistically. However, the vast majority of moles, including atypical ones, never become melanoma. Regular monitoring with a dermatologist, and prompt evaluation of any mole that is changing, is the appropriate response to having multiple moles or atypical moles.

References

1. National Cancer Institute. Melanoma Risk Factors. https://cancer.gov/types/skin/patient/melanoma-treatment-pdq

2. American Academy of Dermatology Association. Melanoma: Causes and Risk Factors. https://www.aad.org/public/diseases/skin-cancer/types/common/melanoma/causes

3. El Ghissassi F, Baan R, Straif K, et al; WHO International Agency for Research on Cancer Monograph Working Group. A review of human carcinogens, part D: radiation. Lancet Oncol. 2009;10(8):751-752. https://pubmed.ncbi.nlm.nih.gov/19655431.

4. Boniol M, Autier P, Boyle P, Gandini S. Cutaneous melanoma attributable to sunbed use: systematic review and meta-analysis. BMJ. 2012;345:e4757. https://pubmed.ncbi.nlm.nih.gov/22833605.

5. Gandini S, Sera F, Cattaruzza MS, et al. Meta-analysis of risk factors for cutaneous melanoma: I. Common and atypical naevi. Eur J Cancer. 2005;41(1):28-44. https://pubmed.ncbi.nlm.nih.gov/15617989

6. Goldstein AM, Tucker MA. Dysplastic nevi and melanoma. Cancer Epidemiol Biomarkers Prev. 2013;22(4):528-532. https://pubmed.ncbi.nlm.nih.gov/23549396.