Melanoma is a cancer that starts in melanocytes, the cells that give your skin its color. It accounts for a small percentage of all skin cancers but causes the majority of skin cancer deaths because of its ability to spread to other organs. Caught early, the five-year survival rate is effectively 100%. Once it reaches distant parts of the body, that number drops to 34%.
How Melanoma Develops
Melanocytes sit in the deepest layer of your epidermis, your skin’s outer shell. Their job is to produce pigment that absorbs ultraviolet light and shields the DNA in surrounding cells. When UV radiation damages a melanocyte’s own DNA beyond repair, the accumulated mutations can flip on growth signals that the cell can no longer turn off. The result is uncontrolled division: cells that keep multiplying, resist normal death signals, and eventually gain the ability to invade deeper tissue.
One key change happens at the cellular level. Normal melanocytes are anchored to neighboring skin cells by a protein called E-cadherin. Melanoma cells lose that anchor and switch to a different adhesion protein, N-cadherin, which lets them detach from the skin’s surface and migrate into blood vessels and lymph nodes. That migration is what makes melanoma dangerous. A mole that stays put is manageable. A melanoma that enters the bloodstream can seed tumors in the lungs, liver, brain, or bones.
Types of Melanoma
Not all melanomas look or behave the same way. The four main subtypes differ in where they appear, how fast they grow, and who they tend to affect.
- Superficial spreading melanoma is the most common type. It starts by growing outward along the top layer of skin before eventually penetrating deeper. It often looks like a flat or slightly raised discolored patch.
- Nodular melanoma is the most aggressive form. Instead of spreading outward first, it grows downward into the skin quickly. Its hallmark is a firm bump or nodule that rises above the skin’s surface.
- Lentigo maligna melanoma tends to appear on the face, scalp, or neck of older adults with years of cumulative sun damage. It typically starts as a flat, slowly expanding patch of uneven color.
- Acral lentiginous melanoma develops on the palms, soles of the feet, or under fingernails and toenails. It is the most common form of melanoma in people of African and Asian descent, though it can affect anyone regardless of race.
Who Is at Higher Risk
UV exposure is the single biggest modifiable risk factor. Sunlight is the main source, but tanning beds and sun lamps carry the same type of radiation. Both cumulative lifetime exposure and intense, blistering sunburns (particularly in childhood) increase risk.
Skin type matters significantly. People with lighter skin are at much higher risk than those with darker skin. Within that group, red or blond hair, blue or green eyes, and skin that freckles or burns easily push the risk higher still. Having a large number of moles, especially irregular or “dysplastic” moles, is another well-established risk factor. People with a condition called familial atypical multiple mole and melanoma syndrome, where many irregular moles run alongside a family history of melanoma, face a very high lifetime risk.
Genetics play a role beyond skin color. A family history of melanoma can reflect shared gene mutations, shared sun habits, or both. A rare inherited condition called xeroderma pigmentosum cripples the skin’s ability to repair UV-damaged DNA, leading to dramatically elevated cancer risk from a young age.
How to Spot It: The ABCDE Rule
The ABCDE framework, developed by the National Cancer Institute, describes the visual features of early melanoma:
- Asymmetry: One half of the mole doesn’t match the other.
- Border: The edges are ragged, notched, or blurred rather than smooth. Pigment may seem to bleed into surrounding skin.
- Color: The color is uneven, with a mix of brown, tan, black, or areas of white, gray, red, pink, or blue.
- Diameter: Most melanomas are larger than 6 millimeters (about the size of a pencil eraser) when diagnosed, though they can be smaller.
- Evolving: The mole has changed in size, shape, or color over weeks or months.
When ABCDE Doesn’t Apply
Nodular melanoma often breaks the rules. Because it grows outward from the skin as a dome-shaped bump rather than spreading as a flat patch, it may look symmetric, have smooth borders, and be a single uniform color. For these lesions, the EFG rule is more useful: Elevated above the skin’s surface, Firm to the touch, and Growing progressively over weeks or months. Any new bump on your skin that feels solid and keeps getting bigger deserves a closer look, even if it doesn’t match the classic ABCDE description.
How Melanoma Is Diagnosed
A suspicious spot is confirmed or ruled out through a biopsy, where a sample of tissue is removed and examined under a microscope. The preferred method when melanoma is suspected is an excisional biopsy, which removes the entire lesion along with a small margin of normal skin around it. This gives pathologists the full picture: the type of melanoma, how deep it has grown, and whether the edges of the removed tissue are cancer-free.
The depth measurement, called Breslow thickness, is the single most important number in determining how serious the melanoma is. It’s measured in millimeters from the top of the skin down to the deepest point the cancer has reached.
Staging and What It Means
Melanoma staging combines the tumor’s thickness with information about whether it has spread to lymph nodes or distant organs. The thickness categories under current guidelines break down this way:
- T1: 1 mm or thinner
- T2: 1.01 to 2 mm
- T3: 2.01 to 4 mm
- T4: thicker than 4 mm
From a practical standpoint, staging groups into three broad categories that predict survival. Localized melanoma, still confined to the original site, carries a five-year survival rate of 100%. Regional melanoma, meaning it has reached nearby lymph nodes, drops to 76%. Distant melanoma, where the cancer has spread to other organs, has a five-year survival rate of 34%. These numbers, drawn from SEER data covering 2016 through 2022, reflect outcomes across all races and both sexes.
The steep drop between localized and distant disease is exactly why early detection matters so much. A thin melanoma caught at T1 is almost always curable with surgery alone. A thick melanoma that has already sent cells to the lungs or brain requires systemic treatment and has a far less certain outcome.
Treatment Options
For early-stage melanoma, surgery is the primary treatment. The goal is to remove the tumor with a clear margin of healthy tissue. For thin melanomas, this is often the only treatment needed.
When melanoma is more advanced or has spread, two categories of drugs have transformed outcomes over the past decade. Immunotherapy drugs work by removing the brakes that cancer cells put on your immune system, allowing your own white blood cells to recognize and attack the tumor. Several checkpoint inhibitors are now FDA-approved for melanoma, including pembrolizumab, nivolumab, and ipilimumab. These can be used alone or in combination.
The second category targets a specific genetic mutation found in roughly half of all melanomas: a change in the BRAF gene. Targeted therapy pairs a BRAF inhibitor with a MEK inhibitor to shut down the signaling pathway that drives tumor growth. These drug combinations tend to shrink tumors rapidly, though the cancer can eventually develop resistance.
The choice between immunotherapy and targeted therapy depends on multiple factors, including whether the melanoma carries a BRAF mutation, how fast the cancer is progressing, and the patient’s overall health. In many cases, immunotherapy is tried first because its responses tend to be more durable. Some patients remain cancer-free for years after finishing treatment.
Reducing Your Risk
Since UV radiation drives the majority of melanomas, consistent sun protection is the most effective prevention strategy. That means broad-spectrum sunscreen, protective clothing, and avoiding tanning beds entirely. These measures are especially important for people with lighter skin, a history of sunburns, or a family history of melanoma.
Regular skin self-exams help catch melanoma when it’s still thin and highly curable. Check your entire body monthly, including areas that don’t get much sun: the soles of your feet, between your toes, under your nails, and your scalp. If you have many moles or a family history of melanoma, annual full-body skin exams with a dermatologist add another layer of protection.