Symptoms of melanoma

Short answer: The main symptom of melanoma is a mole or spot that changes — in size, shape, color, or border — or a new spot that looks different from all your others. The ABCDE rule (Asymmetry, Border, Color, Diameter, Evolving) is the standard checklist, and "Evolving" is the most important letter. Melanoma can also appear where the sun never reaches: under a nail, on the sole of the foot, on the palm, or inside the eye or mouth.

Melanoma is the most dangerous skin cancer, but it's also one of the most visible. Caught while confined to the skin's surface, five-year survival is above 99%. The whole game is noticing a change and getting it looked at within weeks rather than years.

The ABCDE rule

• A — Asymmetry. One half doesn't match the other.
• B — Border. Edges are irregular, notched, scalloped, or blurred.
• C — Color. More than one color, or uneven color — brown, black, tan, red, white, or blue in the same lesion.
• D — Diameter. Larger than 6 mm (about a pencil eraser) — though melanomas can be smaller.
• E — Evolving. Changing in any way over weeks to months: growing, darkening, raising, itching, bleeding, crusting.

Evolving is the one that matters most. A stable, ugly-looking mole you've had for 30 years is far less concerning than a small, ordinary-looking spot that changed in the last three months.

The "ugly duckling" sign

Most of your moles look roughly like siblings. The one that stands out — noticeably darker, larger, or shaped differently from all the rest — is the one to have checked, even if it technically passes the ABCDE test.

Warning signs beyond moles

• A sore that doesn't heal within a few weeks
• A spot that itches, is tender, or bleeds without being scratched
• Pigment spreading from a mole's border into surrounding skin
• A new dark streak under a fingernail or toenail that isn't from an injury (subungual melanoma)
• A new dark spot on the palm, sole, or between the toes (acral melanoma — this type is not sun-related and occurs across all skin tones)
• A firm, dome-shaped, pink or flesh-colored bump that's growing fast (amelanotic melanoma has little or no pigment and is easy to dismiss)
• Vision changes, floaters, or a dark spot on the iris (ocular melanoma)

A note on skin tone

Melanoma is less common in people with darker skin — and more often fatal, because it's diagnosed later. In darker skin it appears most often on the palms, soles, under the nails, and in the mouth. Those are the places to check deliberately.

Who's at higher risk

• Many moles (more than 50), or atypical/dysplastic moles
• Fair skin, light eyes, red or blond hair, freckling, skin that burns easily
• History of blistering sunburns, especially in childhood
• Tanning bed use — significant, and starts young
• Personal or family history of melanoma
• A weakened immune system, or organ transplant
• Certain inherited mutations (CDKN2A)

Risk factors help — but roughly a quarter of melanomas arise on skin with no unusual history at all.

When to see a doctor

Book a dermatologist within a few weeks for:

• Any mole that has changed in the last 3–6 months
• A new spot that looks unlike your others
• A sore that won't heal
• A dark streak under a nail
• Any spot that bleeds or itches persistently

Do not wait for a routine annual visit. A dermatologist can usually fit a "changing mole" in sooner if you use those words when booking.

What the workup looks like

• Full-body skin exam with dermoscopy
• Excisional biopsy — the whole lesion is removed, not shaved or sampled. This matters: a partial biopsy can understate depth.
• Breslow depth — how deep in millimeters the melanoma extends. This is the single most important prognostic number on the pathology report.
• Sentinel lymph node biopsy for deeper lesions
• Molecular testing (BRAF, NRAS, KIT) for advanced disease — it determines targeted therapy eligibility

What to do this week

1. Photograph the spot next to a ruler or coin, with the date. Change over time is the evidence that matters.
2. Book a dermatologist and say the words "a mole that has changed."
3. Check the places you don't normally look — scalp, behind the ears, between toes, soles, nails. Ask someone to check your back.
4. If a biopsy is done, ask for the Breslow depth and what it means.
5. Don't accept "let's watch it for a year" on a spot that's actively changing.

If you're diagnosed, our guide to what to do in the first 72 hours after a cancer diagnosis walks through the order of steps. And if your first appointment left you with a report full of words you don't understand, how to read a pathology report you don't understand is a plain-language walkthrough.

Takeaway: melanoma caught in the skin's top layer is almost always curable. The difference between that and a life-threatening diagnosis is often just a few months of not getting it looked at.

Related reading

• Melanoma guide — the full hub, including what to ask after diagnosis.
• Just diagnosed with cancer: what to do first — the first 72 hours, in order.
• How to read a pathology report you don't understand — including Breslow depth and margins.

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This post is for general informational purposes and isn't a substitute for guidance from your care team. If you have symptoms that concern you, call your doctor.