Skin cancer tool

Is it melanoma, or one of its lookalikes?

Most worrying spots turn out to be something harmless — and a few harmless-looking ones turn out not to be. Compare the twelve things most often confused with melanoma, and see what makes a dermatologist look twice.

What do you think you’re looking at?

Pick the closest match and see it beside melanoma. The drawings are schematic — they show the features a dermatologist compares, not photographs of real lesions.

A common mole

Also called benign nevus

An ordinary mole most adults have somewhere — usually one you've had for years.

Points to common mole

  • Round or oval, and the two halves match if you draw a line through it.
  • One even shade of tan or brown all the way across.
  • A smooth, clearly defined edge.
  • Smaller than a pencil eraser, about 6 mm.
  • It looks much like your other moles, and it has stayed the same for years.

Melanoma

In this comparison

What tends to be different when the same spot is a melanoma.

Points to melanoma

  • The halves don't match, and the edge is notched, scalloped or smudged.
  • Several colours in one spot — browns with black, red, white or blue-grey.
  • It stands out from your other moles. That's the “ugly duckling” sign.
  • It's changing: growing, darkening, itching or bleeding.

Get it checked anyway if

  • It has changed in any way over recent months.
  • It's new, and you're over 30 — most ordinary moles appear before then.
  • It looks unlike every other mole on your body.

This comparison can’t clear your spot. It describes what dermatologists weigh up when two things look alike. Telling them apart for certain takes an examination — usually with a dermatoscope, sometimes a biopsy. If you’re here because something changed, book the appointment.

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The ABCDE checks

The five features dermatologists teach people to watch for. Any one of them is reason enough to have a spot looked at.

A

Asymmetry

Draw a line through the middle. On an ordinary mole the two halves match. On a melanoma they don't.

B

Border

Benign spots stop cleanly. Melanoma edges tend to be notched, scalloped or smudged into the skin around them.

C

Color

One even shade is reassuring. Several shades in one spot — browns with black, red, white or blue-grey — is not.

D

Diameter

Melanomas are often larger than 6 mm, about a pencil eraser, by the time they're found. But plenty are smaller, so size alone never clears a spot.

E

Evolving

The single most useful sign. Any spot that is changing — growing, darkening, itching, bleeding, crusting — should be examined.

And the ugly duckling

Most of your moles look like siblings. A melanoma tends to look like the odd one out — bigger, darker, lighter or just different from the rest. Dermatologists call it the ugly duckling sign, and it catches melanomas that pass the ABCDE checks.

Book an appointment now if any of these apply

  • A spot that is changing in size, shape or colour.
  • A sore that hasn't healed within a few weeks.
  • A spot that bleeds, itches or crusts without an injury to explain it.
  • A mole that looks different from all your others.
  • A new pigmented spot appearing after about age 30.
  • A dark band running the length of a nail, or pigment spreading onto the skin around it.
  • A pink, red or skin-coloured lump that keeps growing — melanoma isn't always brown.
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Every comparison, side by side

The same twelve comparisons in full, so you can read them without clicking through.

Mole vs melanoma

A common mole — also called benign nevus

An ordinary mole most adults have somewhere — usually one you've had for years.

Points to common mole

  • Round or oval, and the two halves match if you draw a line through it.
  • One even shade of tan or brown all the way across.
  • A smooth, clearly defined edge.
  • Smaller than a pencil eraser, about 6 mm.
  • It looks much like your other moles, and it has stayed the same for years.

Points to melanoma

  • The halves don't match, and the edge is notched, scalloped or smudged.
  • Several colours in one spot — browns with black, red, white or blue-grey.
  • It stands out from your other moles. That's the “ugly duckling” sign.
  • It's changing: growing, darkening, itching or bleeding.

Get it checked anyway if

  • It has changed in any way over recent months.
  • It's new, and you're over 30 — most ordinary moles appear before then.
  • It looks unlike every other mole on your body.

More on common mole in the glossary

Dysplastic nevus vs melanoma

An atypical mole — also called dysplastic nevus

A mole that looks irregular under the eye of a dermatologist but is not a cancer. Having many of them raises your melanoma risk.

Points to atypical mole

  • Larger than most of your moles, often 6 mm or more.
  • An edge that fades into the surrounding skin rather than stopping sharply.
  • Usually two shades of brown rather than a jumble of colours.
  • It has looked this way for a long time without changing.

Points to melanoma

  • Colours beyond brown — black, red, white or blue-grey in one spot.
  • Change you can date: it looked different six months ago.
  • One mole that stands apart from the rest of your atypical moles.

Get it checked anyway if

  • You have ten or more atypical moles — that carries a much higher melanoma risk and is a reason for regular skin checks.
  • Any one of them starts changing.
  • You have a personal or family history of melanoma.

More on atypical mole in the glossary

Freckle vs melanoma

A freckle — also called ephelis

Small flat spots that come out with sun and fade in winter.

Points to freckle

  • Small — usually only a few millimetres.
  • They come in groups across sun-exposed skin, not one on its own.
  • Light tan to brown, all much the same shade as each other, and usually under 3 mm.
  • They darken in summer and fade in winter. A sun spot doesn't — it stays put year round.
  • Common in fair skin, especially with red hair, and present since childhood.

Points to melanoma

  • A single spot that's darker or larger than everything around it.
  • It doesn't fade with the seasons.
  • It keeps getting bigger, or takes on more than one colour.

Get it checked anyway if

  • One “freckle” is clearly outgrowing or outdarkening its neighbours.
  • A new one appears in adulthood and keeps changing.

Sun spot vs melanoma

A sun spot — also called solar lentigo, age spot, liver spot

Flat brown patches from years of sun, usually on the hands, forearms, face and shoulders.

Points to sun spot

  • One even colour throughout — tan, brown or nearly black, but all one shade.
  • A clearly defined edge.
  • Flat, or barely raised.
  • On skin that has had years of sun: backs of the hands, forearms, upper back, face.
  • Common from middle age onward, and usually several of them at once.

Points to melanoma

  • Several shades in one patch, especially grey or black mixed through the brown.
  • An edge that's uneven or fading away in one direction.
  • It's slowly spreading, while your other sun spots stay put.

Get it checked anyway if

  • One spot on your face or neck is slowly widening over months or years — that's how lentigo maligna behaves, and it's easy to dismiss as an age spot.
  • Any part of it darkens, thickens or takes on a grey tone.

Seborrheic keratosis vs melanoma

A seborrheic keratosis — also called senile wart, barnacle of ageing

Warty, waxy growths that look stuck on the skin. Extremely common with age and entirely benign.

Points to seborrheic keratosis

  • A waxy, “stuck-on” look, as if it would come off with a fingernail.
  • A rough, warty surface rather than smooth skin.
  • Anywhere from pale tan to black, but evenly so.
  • Often several, on the chest, back, face or neck — never on palms or soles.
  • They thicken slowly over years.

Points to melanoma

  • Flat rather than stuck-on and warty.
  • Colour that varies across the spot.
  • Faster change — months rather than years.

Get it checked anyway if

  • It has bled, or it itches persistently.
  • One growth looks different from your other seborrheic keratoses. A pigmented melanoma can hide among them, and telling them apart can need a dermatoscope.

More on seborrheic keratosis in the glossary

Cherry angioma vs melanoma

A cherry angioma — also called cherry spot, Campbell de Morgan spot

A small bright red dome made of tiny blood vessels. Harmless.

Points to cherry angioma

  • Bright red, purple or blue rather than brown or black.
  • Small and dome-shaped, usually under a centimetre.
  • Smooth and even, with a clean edge.
  • You have several, and they've increased in number since your forties.

Points to melanoma

  • Brown, black or multi-coloured rather than uniformly red.
  • It keeps growing, and may bleed or crust.
  • A nodular melanoma can be firm, raised and growing week to week.

Get it checked anyway if

  • One has turned dark or black — a clotted angioma can look just like a nodular melanoma, and a dermatoscope settles it in seconds.
  • It's growing, bleeding repeatedly or changing shape.

Dermatofibroma vs melanoma

A firm little nodule in the skin, usually on the lower leg, often after a bite or minor injury.

Points to dermatofibroma

  • Firm, like a small lentil under the skin.
  • It dimples inward when you pinch the skin either side of it — the dimple sign.
  • Usually 0.5–1.5 cm, most often on the lower legs.
  • Pink to light brown in fair skin, dark brown in darker skin, but one shade.
  • It has sat there unchanged for years.

Points to melanoma

  • It rises above the skin rather than dimpling in.
  • Uneven colour and an uneven edge.
  • It's growing month by month.

Get it checked anyway if

  • It's growing, or the colour has become patchy.
  • It isn't behaving like your others — rarely, tumours that need treatment can look similar.

Blood blister vs melanoma

A pocket of blood under the skin after a pinch, rub or knock.

Points to blood blister

  • You can name the cause: new shoes, a pinch, a tool, a knock.
  • It appeared suddenly, within hours of that.
  • It's tender or throbbing — early melanoma usually isn't.
  • It settles and disappears within about two weeks.
  • Dark red or purple, with a raised blister roof over it.

Points to melanoma

  • No injury that explains it.
  • It doesn't resolve — after two weeks it's still there, or bigger.
  • It's painless but keeps growing, and may bleed or crust.

Get it checked anyway if

  • It hasn't healed within two weeks.
  • It came back in the same place without a fresh injury.
  • It's on the sole, palm or under a nail, where melanoma is easy to miss.

Black spot under nail vs melanoma

A bruise under the nail — also called subungual hematoma

Blood trapped under the nail after crushing it, stubbing it, or running in tight shoes.

Points to bruise under the nail

  • It followed an injury, or repeated pressure from shoes.
  • It looks like a smudge or blotch, not a clean stripe.
  • It grows out with the nail — the mark moves toward the tip over weeks and a clear nail appears behind it.
  • It changes colour as it ages, like any bruise.

Points to melanoma

  • A dark brown or black band running the length of the nail, from cuticle to tip.
  • It stays put as the nail grows, and the band widens — usually at the cuticle end first.
  • Pigment spreads onto the skin around the nail. That's Hutchinson's sign.
  • Most often the thumb, index finger or big toe.

Get it checked anyway if

  • There was no injury you can remember.
  • Months later it hasn't moved down the nail.
  • The band is widening, or the nail is splitting or lifting.

Basal cell carcinoma vs melanoma

Basal cell carcinoma — also called BCC

The most common skin cancer. It grows slowly and very rarely spreads — but it is a cancer and needs treating.

This is itself a skin cancer, not a harmless lookalike. It needs treatment.

Points to Basal cell carcinoma

  • A shiny, pearly bump you can see light catching.
  • Fine blood vessels running across the surface.
  • A rolled edge around a dip or sore in the middle.
  • A sore that heals, breaks down and heals again over months.
  • On the most sun-exposed skin: nose, cheeks, ears, scalp.

Points to melanoma

  • Usually pigmented and flat rather than pearly and raised.
  • Melanoma changes faster and can spread, which is why it's the more urgent of the two.
  • A BCC can also be brown or black, so colour alone doesn't separate them.

Get it checked anyway if

  • This one isn't a lookalike to be reassured by — a basal cell carcinoma needs treatment. Book an appointment.

More on Basal cell carcinoma in the glossary

Squamous cell carcinoma vs melanoma

Squamous cell carcinoma — also called SCC

The second most common skin cancer. It can spread if left, so it needs treating promptly.

This is itself a skin cancer, not a harmless lookalike. It needs treatment.

Points to Squamous cell carcinoma

  • A scaly or crusted lump that keeps enlarging.
  • Often tender or sore to touch.
  • It grows over weeks to months, faster than most benign growths.
  • On sun-exposed skin: face, lips, ears, hands, forearms, lower legs.
  • It often starts in a rough, pre-cancerous patch (an actinic keratosis).

Points to melanoma

  • Usually pigmented, and usually flat in its early stages.
  • Melanoma is less likely to be scaly or tender.

Get it checked anyway if

  • This one isn't a lookalike to be reassured by either — a squamous cell carcinoma needs treatment, and sooner rather than later. Book an appointment.

More on Squamous cell carcinoma in the glossary

Lentigo maligna vs age spot

Lentigo maligna — also called the sun spot that isn't

An early melanoma that looks like an ordinary age spot and grows for years before it's noticed. The most important entry on this page.

This is itself a skin cancer, not a harmless lookalike. It needs treatment.

Points to Lentigo maligna

  • It is a melanoma — an early one, confined to the top layer of skin, where it is highly treatable.
  • A flat patch on the face or neck that has been slowly widening for years.
  • Several shades mixed together, often with grey.
  • An edge that fades away unevenly into sun-damaged skin.
  • Most common over 60, in people with years of outdoor sun.

Points to melanoma

  • Other melanomas usually change over months, not years — which is why this one gets dismissed.
  • If it becomes invasive it's called lentigo maligna melanoma, and the outlook changes.

Get it checked anyway if

  • You have a facial patch that's slowly grown over years and you'd assumed it was an age spot. That is the classic history. Get it examined.

More on Lentigo maligna in the glossary

Common questions

What's the difference between a sun spot and melanoma?
A sun spot (solar lentigo) is one even shade of brown with a clearly defined edge, sits on skin that's had years of sun, and usually comes with several others like it. Melanoma more often mixes several shades in one spot — brown with black, grey, red or white — and has an uneven or fading edge. The catch is lentigo maligna, an early melanoma that looks like an ordinary age spot on the face and widens slowly over years. If a facial patch has quietly grown, have it examined rather than assuming it's age.
Can a blood blister be melanoma?
A true blood blister follows an injury, appears within hours, is usually tender, and settles within about two weeks. A nodular melanoma can look very similar at first, but there's no injury to explain it, it's usually painless, and it keeps growing rather than healing. The two-week rule is the practical one: anything blood-blister-like that hasn't resolved in two weeks should be looked at, particularly on a palm, sole or under a nail.
Is a dark line under my nail melanoma?
Usually it's a bruise, especially if you crushed or stubbed the nail or run in tight shoes. A bruise looks like a smudge and travels toward the tip as the nail grows, leaving clear nail behind it. Nail melanoma is a brown or black band running the full length of the nail that stays put as the nail grows and widens over time, most often on a thumb, index finger or big toe. Pigment spreading onto the skin around the nail — Hutchinson's sign — needs prompt assessment.
How can I tell a seborrheic keratosis from melanoma?
Seborrheic keratoses have a waxy, warty, stuck-on look, as though you could lift them off, and most people who have one have several. Melanoma is usually flat in its early stages with colour that varies across the spot. They can be genuinely hard to separate by eye when a keratosis is very dark, which is what a dermatoscope is for — so a single growth that looks unlike your others is worth showing someone.
Does a spot have to be bigger than 6 mm to be melanoma?
No. The 6 mm guideline in the ABCDE list describes how large melanomas often are when they're found, not a threshold below which a spot is safe. Melanomas are regularly diagnosed smaller than that. Change matters far more than size: a small spot that is growing, darkening, itching or bleeding should be examined whatever its diameter.
Can melanoma be skin-coloured or pink?
Yes. Amelanotic melanoma has little or no pigment and can look pink, red, skin-coloured or even clear, which is why it's often mistaken for a harmless bump and diagnosed late. A pink lump that keeps growing, bleeds or won't heal deserves the same attention as a changing brown spot.
Can this tool tell me whether my spot is melanoma?
No, and it doesn't try. It explains what dermatologists look at when they compare melanoma with the spots it resembles, so you can describe yours better and decide whether to come in. A diagnosis needs an in-person examination, usually with a dermatoscope, and sometimes a biopsy — which is the only way to be certain.

Where this comes from

Clinical descriptions on this page are drawn from these references.

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