Understanding melanoma: The signs and risk factors
Learn more about how to monitor your skin for melanoma and ways to help prevent it
March 26, 2025
What is melanoma?
Melanoma is a form of skin cancer. Characterized by the uncontrolled growth of pigment-producing cells, melanoma accounted for approximately 1.7% of new cancer cases worldwide in 2022.
Exposure to ultraviolent (UV) radiation, either from the sun or other sources such as tanning beds and sunlamps, is a major risk factor for skin cancers, including melanoma. While melanoma can occur anywhere on the skin, including areas without sun exposure, it’s more likely to start in certain locations, like the face and neck, legs (most common in women), and chest and back (most common in men).
The risk of melanoma generally increases with age and incidence is greater among older populations. However, even among patients younger than 30 years, melanoma is one of the most common cancers, especially in young women.
Worldwide, the melanoma diagnosis rate has risen over the past two decades
331,000+
Estimated number of new melanoma cases worldwide in 2022
Signs of cancerous moles
A new spot on the skin or a spot that is changing in size, shape or color, or one that looks different, is an important warning sign of melanoma and should be checked by a doctor. The ABCDE rule can be used as a guide to help identify the warning signs of melanoma:
A is for Asymmetry
One half of a mole or spot does not match the other.
B is for Border
The edges of the spot are irregular, scalloped or poorly defined.
C is for Color
The color of the spot is not the same all over and may include different shades of brown or black, sometimes with patches of pink, red, white or blue.
D is for Diameter
The spot is larger than 6 millimeters across. Melanoma is usually larger than 6 millimeters in size (about 1/4-inch or the size of a pencil eraser) when diagnosed. However, it can sometimes be smaller.
E is for Evolving
The mole is changing in size, shape, or color.
Any of these warning signs should be discussed with a doctor, especially if you feel you are at risk for melanoma.
Causes of melanoma
There are many risk factors and causes of melanoma, including:
- UV light on your skin, such as from the sun or a tanning bed (the most common risk factor for most cases of melanoma)
- Age — melanoma is more common in older people, but younger people are also at risk. Melanoma is one of the most common cancers in people younger than 30 years (especially among women)
- Moles — having many moles, irregular or large moles, or atypical moles
- Personal or family history – Melanoma can be genetic and having a relative with melanoma can increase your risk
- Fair skin or a fair complexion, a lot of freckles and/or light-colored hair and eyes
Ways to lower your risk of melanoma
Melanoma can’t be entirely prevented, but there are ways to lower your risk. The number one way to lower risk is to protect against UV rays, which damage the DNA of skin cells and impact the genes that control skin cell growth. That’s why it’s important to avoid tanning beds, booths, sunlamps and other artificial sources of UV radiation. However, the top source of UV rays is the sun. That’s why it’s important to practice sun safety every time you go outside, even on cloudy days when UV rays can still shine through. Here are a few ways to protect yourself:
Seek shade
UV exposure is greatest between the hours of 10 a.m. and 4 p.m. If you need to be outside during these hours, seek shade – under a tree, an umbrella or an awning.
Wear a hat
Try to find a hat with a wide brim – at least 2 or 3 inches wide – to protect your face, top of the head, ears and neck.
Cover up
Choose clothing with a tight knit or weave, and avoid shirts that you can see through. Remember, if light is getting through, then UV rays are too.
Use sunscreen
For extended outdoor activity, use a water-resistant, broad spectrum sunscreen with an SPF of 30 or higher.
Wear sunglasses
Protect your eyes and the sensitive skin around them. Pick a pair of sunglasses that will block as close to 100 percent of both UVA and UVB rays as possible.
