Melanoma is a cancer that starts in melanocytes, the cells that make the pigment in your skin

Melanoma begins when melanocytes grow in an uncontrolled way. These cells normally produce melanin, the substance that gives your skin its color and protects it from sun damage. When melanocytes become cancerous, they can spread to other parts of your body—lymph nodes, lungs, liver, brain, and bone. This ability to spread is what makes melanoma more serious than the other two common types of skin cancer: basal cell carcinoma and squamous cell carcinoma.

Not all melanomas look the same or behave the same way. Some grow slowly over years; others grow quickly over weeks or months. The depth of the melanoma in your skin and whether it has spread are the main factors that determine how serious it is and what treatment you will need.

Key Takeaways

  • Melanoma starts in pigment-producing cells and can spread to other organs, which is why it is considered more dangerous than basal cell or squamous cell skin cancer.
  • The ABCDE rule—asymmetry, border irregularity, color variation, diameter larger than a pencil eraser, and evolving or changing—helps you spot a spot that may be melanoma.
  • Depth (called Breslow thickness) and whether the cancer has spread determine the stage and what treatment options exist.
  • A skin biopsy is the only way to confirm melanoma; a dermatologist removes a sample and sends it to a lab for examination.

How melanoma differs from other skin cancers

The three main types of skin cancer are basal cell carcinoma, squamous cell carcinoma, and melanoma. Basal cell and squamous cell cancers start in different layers of skin and rarely spread beyond the skin itself. Melanoma is different: it has a much higher risk of spreading to distant parts of your body, even when caught early.

Melanoma accounts for only about 1 in 20 skin cancers, but it causes the majority of skin cancer deaths because of its ability to metastasize—travel through the bloodstream or lymph system to other organs. This is why finding it early makes such a difference in treatment options and outcomes.

The ABCDE warning signs

Dermatologists teach the ABCDE rule to help people spot melanomas before they spread. A stands for asymmetry: one half of the spot does not match the other half. B is border irregularity: the edges are ragged, notched, or blurry rather than smooth. C is color variation: the spot contains multiple colors—brown, black, tan, red, or even white—rather than one uniform shade.

D is diameter: the spot is larger than a pencil eraser (about 6 millimeters). E is evolving or changing: the spot has grown, changed color, or changed shape over weeks or months. Any spot that meets one or more of these criteria should be examined by a dermatologist. A spot does not have to be large or dark to be melanoma; some melanomas are small, light-colored, or even colorless.

How melanoma is diagnosed

A dermatologist cannot tell whether a spot is melanoma just by looking at it. The only way to confirm melanoma is with a skin biopsy. The doctor removes all or part of the suspicious spot and sends it to a pathology lab, where a pathologist examines the cells under a microscope to see whether cancer is present.

If the biopsy shows melanoma, the pathologist also measures how deep the cancer goes into the skin (called Breslow thickness) and whether it has certain high-risk features. These measurements determine the stage of the melanoma and guide decisions about what happens next—whether you need surgery alone, surgery plus other treatments, or monitoring.

Stages of melanoma and what they mean

Melanoma is staged from 0 to 4, based on depth and spread. Stage 0 melanoma is confined to the outermost layer of skin and has not invaded deeper layers. Stage 1 and 2 melanomas are in the skin but have not spread to lymph nodes or distant organs; the difference between them is thickness. Stage 3 means the cancer has spread to nearby lymph nodes or skin. Stage 4 means it has spread to distant organs like the lungs, liver, or brain.

The stage determines your treatment path. Early-stage melanomas (0, 1, and most 2s) are usually treated with surgery to remove the cancer and a margin of healthy skin around it. Higher stages may require additional surgery to remove affected lymph nodes, plus systemic treatments like immunotherapy or targeted therapy that work throughout the body.

Risk factors that increase your chance of melanoma

Ultraviolet (UV) radiation from the sun or tanning beds is the primary risk factor for melanoma. People with fair skin, light hair, and light eyes are at higher risk because they have less melanin to protect against UV damage. A history of severe sunburns, especially in childhood, raises risk significantly.

Other risk factors include a family history of melanoma, a personal history of melanoma or other skin cancer, a large number of moles, or atypical moles (moles that are irregular in shape or color). Having one or more risk factors does not mean you will develop melanoma, but it means you should have your skin checked regularly by a dermatologist and monitor your own skin for changes.

What happens after a melanoma diagnosis

After melanoma is confirmed and staged, your doctor will discuss treatment options based on the stage and your overall health. Early-stage melanomas are often cured with surgery alone. More advanced melanomas may require additional treatments, and your doctor may refer you to an oncologist (a cancer specialist) to discuss options like immunotherapy, targeted therapy, or clinical trials.

You will also need follow-up appointments to monitor for recurrence. The schedule depends on the stage: early-stage melanomas may need skin checks every few months for the first year or two, then less frequently. Your doctor will also teach you how to do monthly self-checks of your skin and what changes to report.

Frequently Asked Questions

Can you get melanoma from a sunburn?

Sunburns do not cause melanoma directly, but repeated or severe UV exposure—including sunburns—increases your risk over time. A single bad sunburn does not mean you will develop melanoma, but it does damage skin cells and raises your lifetime risk, especially if you had severe sunburns in childhood.

Is melanoma always fatal?

No. Early-stage melanomas have high survival rates, especially when caught before they spread to lymph nodes or distant organs. Stage 1 melanomas have a five-year survival rate above 90 percent. Even advanced melanomas are now treated with newer drugs that can extend survival and improve quality of life, though outcomes vary by individual.

Can melanoma come back after treatment?

Yes, melanoma can recur, which is why follow-up monitoring is important. Recurrence can happen in the skin near the original site, in lymph nodes, or in distant organs. Regular skin checks and reporting any new or changing spots to your doctor help catch recurrence early, when treatment is most effective.

What is the difference between a mole and melanoma?

Most moles are benign (not cancer) and stay the same size, shape, and color throughout your life. Melanoma typically shows changes over time—growing, darkening, or becoming irregular. Use the ABCDE rule to monitor your moles. Any mole that changes or meets the ABCDE criteria should be examined by a dermatologist.