Melanoma is a cancer that starts in melanocytes, the cells in your skin that produce pigment. These cells normally protect you by making melanin, the substance that darkens your skin in response to sunlight. When melanocytes accumulate enough DNA damage, they can begin growing uncontrollably and form a tumor. Melanoma accounts for a small fraction of all skin cancers, but it’s the most dangerous type because it can spread to other organs. Globally, about 332,000 people are diagnosed each year, and roughly 58,700 die from it.
How Melanoma Develops
Melanocytes sit in the outermost layer of your skin, the epidermis. Each one contains specialized structures that manufacture melanin and distribute it to surrounding skin cells, forming a shield against ultraviolet radiation. When UV light damages the DNA inside a melanocyte, the cell usually repairs itself or dies off. But if enough mutations accumulate, particularly in genes that control cell growth, the melanocyte can start dividing without the normal safety checks. That uncontrolled growth is melanoma.
An estimated 60 to 70 percent of melanomas are caused by UV radiation exposure. But some melanomas appear in places the sun rarely touches, like the soles of your feet, inside your mouth, or under a fingernail. These forms have different genetic drivers and aren’t linked to sun exposure at all.
Major Risk Factors
UV radiation is the biggest modifiable risk factor. Cumulative exposure from sunlight or tanning beds causes DNA damage, oxidative stress, and inflammation in the skin. Childhood sunburns may double the risk of melanoma later in life, and using indoor tanning before age 30 raises the risk by 75 percent. These numbers reflect how vulnerable developing skin is to lasting damage.
Your natural coloring also matters. People with fair skin, red hair, and freckles often carry a genetic variation that limits production of the more protective type of melanin. This leaves their melanocytes more vulnerable to UV damage. However, some versions of that same gene increase melanoma risk regardless of hair color or skin type, which means darker-skinned people are not immune.
Family history plays a role in roughly 3 to 15 percent of melanoma cases, where inherited gene mutations drive the cancer independent of sun exposure. Having a large number of moles is another well-established risk factor, since UV-induced mutations can accumulate as normal moles transform into melanoma over time.
What Melanoma Looks Like
The most common form, superficial spreading melanoma, appears as a flat, irregularly shaped lesion with brown or black coloring. It tends to grow outward across the skin surface before pushing deeper, which is why catching it early matters so much.
Nodular melanoma looks different. It typically shows up as a smooth, raised, well-defined bump that’s usually dark but can sometimes lack pigment entirely. Because it grows downward into the skin rather than spreading sideways, it can become dangerous faster.
Lentigo maligna melanoma is a large, slowly growing flat patch with blurry, irregular borders. It most often develops on chronically sun-damaged skin, like the face or forearms of older adults. Acral lentiginous melanoma appears on the palms, soles, or under the nails. It can look like a wound, a wart, a bruise, or a pigmented stripe on a nail, which makes it easy to overlook. This is the most common type of melanoma in people with darker skin tones.
Mucosal melanoma is the rarest and most aggressive form. It develops on the moist lining tissues inside the body: the nasal cavity, mouth, digestive tract, or genital areas. Because these locations are hidden and sun exposure isn’t a factor, it’s often caught late. The five-year survival rate for mucosal melanoma is just 14 percent.
The ABCDE Rule for Spotting It
The National Cancer Institute uses a five-feature checklist to help people recognize suspicious spots:
- Asymmetry: One half of the mole doesn’t match the other.
- Border: The edges are ragged, notched, or blurred, and pigment may bleed into surrounding skin.
- Color: The mole has uneven shades of black, brown, tan, or unexpected colors like white, gray, red, pink, or blue.
- Diameter: The spot is larger than about 6 millimeters (roughly the size of a pencil eraser), though melanomas can be smaller.
- Evolving: The mole has visibly changed in size, shape, or color over recent weeks or months.
Not every melanoma will check all five boxes, and some won’t check any. Amelanotic melanomas, which lack pigment, can appear pink or skin-colored and easily fool both patients and doctors. Any new or changing spot that doesn’t heal or looks different from your other moles is worth having examined.
How Depth Determines Stage
Once a melanoma is biopsied, one of the most important measurements is called Breslow thickness. It measures how deep the tumor has grown into the skin, from the surface (or the base of any ulceration) down to the deepest cancer cells. A thinner tumor means an earlier stage and a better prognosis. Thicker tumors are more likely to have reached blood vessels or lymph nodes, which is how melanoma spreads to distant organs like the lungs, liver, or brain.
Staging also considers whether the tumor is ulcerated (the skin over it has broken down), whether cancer cells have reached nearby lymph nodes, and whether it has spread to other parts of the body.
Survival Rates by Stage
Melanoma caught early is highly treatable. Based on data from 2015 to 2021, five-year survival rates break down sharply by how far the cancer has spread:
- Localized (still within the skin): greater than 99 percent
- Regional (spread to nearby lymph nodes): 76 percent
- Distant (spread to other organs): 35 percent
That 35 percent for distant melanoma is actually a significant improvement over what it was a decade ago, largely thanks to newer treatments. But the gap between localized and distant melanoma makes the case for early detection better than almost any statistic can.
How Melanoma Is Treated
For thin, early-stage melanoma, surgery to remove the tumor with a margin of healthy skin around it is often the only treatment needed. As depth and stage increase, additional options come into play.
Immunotherapy has transformed the treatment of advanced melanoma. These drugs work by releasing the brakes on your immune system so it can recognize and attack cancer cells. Checkpoint inhibitors are now a standard part of treatment for melanoma that has spread or is at high risk of returning, and they’re increasingly used after surgery to reduce the chance of recurrence.
Targeted therapy is an option for patients whose tumors carry specific gene mutations. Roughly half of all melanomas have a mutation in a gene called BRAF, and drugs that block BRAF and a related pathway can shrink these tumors rapidly. These are typically given as pill combinations, and they work only in tumors with the matching mutation, so genetic testing of the tumor is a routine step.
For patients with advanced disease, treatment may involve a combination of immunotherapy and targeted therapy, sometimes in sequence. Response varies widely. Some people achieve long-lasting remissions, while others see limited benefit. Side effects range from manageable fatigue and skin reactions to more serious inflammation in organs like the lungs, liver, or intestines, which requires close monitoring.
Reducing Your Risk
Since UV radiation drives the majority of melanomas, sun protection is the most effective prevention strategy. Both the American Academy of Dermatology and the Canadian Dermatology Association recommend broad-spectrum sunscreen with an SPF of at least 30 for people of all skin types. Sunscreen provides protection immediately after application, though waiting 15 to 30 minutes is still advisable if you’ll be in the water. Reapplication is most important after sweating, swimming, or friction from towels, clothing, or sand, rather than on a strict two-hour timer.
Clothing adds a reliable layer of defense. Thicker, tightly woven fabrics in darker colors block more UV radiation. Wet or stretched clothing loses some of its protective ability. Wide-brimmed hats and wraparound sunglasses with UV protection cover the areas sunscreen tends to miss. Seeking shade when the UV index is above 3, typically between late morning and mid-afternoon during warmer months, cuts exposure during peak hours.
For infants under six months, sunscreen is not recommended. Sun avoidance and protective clothing are the primary strategies at that age. For everyone else, the most important habit is simply paying attention to your skin. Familiarity with your own moles and spots makes it far easier to notice when something changes.