How to Tell If a Mole Might Be Melanoma

The ABCDE rule for a suspicious mole

The most widely taught way to size up a mole is the ABCDE rule: Asymmetry (one half unlike the other), Border (ragged, notched, or blurred edges), Color (more than one shade, or uneven color), Diameter (larger than a pencil eraser, about 6 millimeters), and Evolving (any change over time). A mole that fits several of these — above all one that is changing — is worth having examined 1Ref 1Tsao H, Olazagasti JM, Cordoro KM, et al. (2015).Early detection of melanoma: reviewing the ABCDEs.The ABCDE criteria (Asymmetry, Border, Color, Diameter, Evolving) are clinical features supporting early detection of melanoma..

The letter E, for evolving, was added to the original ABCD checklist precisely because change is such a strong signal that something is different about a mole 2Ref 2Abbasi NR, Shaw HM, Rigel DS, et al. (2004).Early diagnosis of cutaneous melanoma: revisiting the ABCD criteria.The ABCD criteria were expanded to ABCDE by adding 'Evolving' because change over time is an important warning feature; the >6 mm diameter criterion is retained but limited.. Growth, darkening, a new color, rising off the skin, or new itching or bleeding all count as evolution.

Two cautions keep the rule honest. No single letter is diagnostic; the ABCDEs are a prompt to look closer, not a score that decides anything. And diameter is the weakest criterion — many melanomas are found smaller than 6 millimeters — so a small mole that is asymmetric, multicolored, or changing still counts 2Ref 2Abbasi NR, Shaw HM, Rigel DS, et al. (2004).Early diagnosis of cutaneous melanoma: revisiting the ABCD criteria.The ABCD criteria were expanded to ABCDE by adding 'Evolving' because change over time is an important warning feature; the >6 mm diameter criterion is retained but limited..

It helps to picture each letter concretely. Asymmetry means that if you drew a line through the middle, the two halves would not match. A troubled border looks like a coastline — notched, scalloped, or fading into the surrounding skin rather than a clean edge. Color means several shades of tan, brown, or black, sometimes with red, white, or blue mixed in. Diameter is a rough flag, not a cutoff. And evolving is any change you or a photo can document over time.

Change over time is the single most important warning sign in a mole.

The ugly-duckling sign

A useful complement to the ABCDEs is the ugly-duckling sign: most of a person's moles resemble one another, so the mole that stands out — darker, larger, differently shaped, or simply 'not like the others' — deserves a closer look. It is valuable because it does not depend on measuring any single mole. It uses your own skin as the reference.

This matters most for people with many moles, where checking each one against a rulebook is impractical. The eye is good at spotting an outlier, and the outlier is the mole more likely to matter. A mole with more than one color, or one that looks out of step with its neighbors, is exactly the kind the ugly-duckling idea is meant to catch.

Like the ABCDEs, it flags rather than diagnoses. A mole can look like the odd one out for entirely benign reasons, and a dangerous mole can sometimes blend in. The sign narrows where to look; it does not settle what a spot is.

In practice, the ugly-duckling test and the ABCDEs work best together. The ABCDEs describe the features of one mole; the ugly-duckling sign compares that mole to the crowd. A spot that fails on its own features and also looks nothing like your others is doubly worth checking — and either signal alone is reason enough for a closer look.

What a normal mole usually looks like

Most moles are harmless, and knowing what an ordinary one looks like makes an unusual one easier to spot. A typical benign mole is roughly round or oval, evenly colored in a single shade of tan or brown, smaller than a pencil eraser, and — importantly — stable, looking much the same month after month and year after year. Many first appear in childhood or early adulthood.

Ordinary moles can be flat or raised, smooth or slightly bumpy, and it is normal to have anywhere from a few to several dozen. What they tend to share is consistency: they resemble one another, and each one holds steady over time. A mole that has looked the same for twenty years is behaving exactly the way benign moles behave.

But these are descriptions of a category, not a test you can apply to your own spot to clear it. A mole can look textbook-normal and still be changing in a way that matters, and some melanomas are small, flat, or a single even color. So 'it looks like a normal mole' is a starting point, never a diagnosis — a normal-looking mole that is new or changing still deserves a look.

Melanoma does not always look the way you expect

Not every melanoma is a large, dark, irregular mole. Some are a single even color; some are flat and never rise above the skin; some are pink, red, or skin-colored with almost no pigment at all; some grow as a fast, firm bump; and some appear under a nail or on a palm or sole. Relying only on the classic dark-and-irregular picture misses these 3Ref 3National Cancer Institute (PDQ Adult Treatment Editorial Board) (2025).Melanoma Treatment (PDQ®)–Health Professional Version.Melanoma has varied presentations and subtypes (including nodular, amelanotic, and acral/subungual) and is diagnosed and staged pathologically, with thickness guiding treatment..

A few patterns are worth knowing by name so they are not dismissed:

• Nodular melanoma grows down into the skin and up out of it quickly, and can be a uniform color. A shorthand for it is EFG — Elevated, Firm, and Growing — because it may not follow the ABCDEs at all.
• Amelanotic melanoma carries little or no pigment and can look like a pink or red spot or a bump that will not heal.
• Flat melanoma stays level with the skin, so 'it isn't raised' is not reassurance.
• Subungual melanoma shows up as a dark streak under a fingernail or toenail.

The point of listing these is not to help you diagnose them, but to explain why 'it doesn't look like the pictures' is not a reason to relax. It is a reason to photograph the spot and have it seen.

This is also why a mark on a palm, a sole, or under a nail should not be brushed off. Acral and subungual melanomas — a dark streak under a fingernail, a new dark patch on a sole — are easy to overlook precisely because they don't sit among your other moles, and they turn up in every skin tone. The lesson across all of these forms is the same: an unusual appearance is a reason to check, never a reason to relax.

What raises your risk

Some people carry a higher baseline risk and have more reason to watch their skin closely: fair skin that burns easily, red or blond hair and light eyes, a history of blistering sunburns, many moles or atypical (dysplastic) moles, a personal or family history of melanoma, and a weakened immune system. Knowing you sit in a higher-risk group changes how carefully you look, not whether a changing mole matters.

The one large risk factor you can change is ultraviolet exposure — from the sun and from tanning beds and sunlamps. Avoiding excess UV is the best-supported way to lower skin-cancer risk 4Ref 4National Cancer Institute (PDQ Screening and Prevention Editorial Board) (2025).Skin Cancer Prevention (PDQ®)–Health Professional Version.Ultraviolet radiation from the sun, sunlamps, and tanning beds is a modifiable risk factor for skin cancer..

A point that surprises many people: melanoma is not limited to sun-exposed skin or to fair skin. It occurs in every skin tone, and in darker skin it more often appears on the palms, soles, and under the nails. Higher risk is a reason for attention, not alarm — most moles in most people are benign — but it is the backdrop against which a new or changing spot should be read.

Risk factors tend to stack rather than cancel. Someone with fair skin, a family history, and many atypical moles carries more reason to watch closely than any one of those factors alone. And a higher-risk person gains the most from knowing their own baseline, because the whole point is to notice when a single spot steps out of line — which is far easier when you already know what your skin normally looks like.

How common is melanoma, and why timing matters

Melanoma is one of the more common cancers in the United States, with well over 100,000 new cases estimated each year 5Ref 5National Cancer Institute, Surveillance, Epidemiology, and End Results (SEER) Program (2025).Cancer Stat Facts: Melanoma of the Skin.US melanoma epidemiology: estimated new cases per year and five-year relative survival that is very high for localized disease and far lower for distant disease.. It is also a cancer where timing changes almost everything about the outlook, which is the entire reason a changing mole is worth acting on rather than watching.

When melanoma is found while it is still confined to the skin, five-year relative survival is very high; once it has spread to distant organs, survival falls dramatically 5Ref 5National Cancer Institute, Surveillance, Epidemiology, and End Results (SEER) Program (2025).Cancer Stat Facts: Melanoma of the Skin.US melanoma epidemiology: estimated new cases per year and five-year relative survival that is very high for localized disease and far lower for distant disease.. Early, thin melanoma is often treated with surgery alone, while advanced melanoma is far harder to treat. Five-year relative survival is over 99% when melanoma is caught before it spreads, and far lower once it reaches distant sites 5Ref 5National Cancer Institute, Surveillance, Epidemiology, and End Results (SEER) Program (2025).Cancer Stat Facts: Melanoma of the Skin.US melanoma epidemiology: estimated new cases per year and five-year relative survival that is very high for localized disease and far lower for distant disease..

That gap is not an argument for panic — it is an argument for not sitting on a spot that is changing. The moles that get people into trouble are usually the ones that were noticed and then ignored, not the ones no one ever saw. The stages of melanoma, from thin and local to advanced, are what these survival differences track.

None of these numbers describe any single person, and a diagnosis is not a prognosis. But the pattern is consistent enough to act on: the earlier a melanoma is found, the simpler the treatment and the better the odds. In practice, 'earlier' almost always means catching a change before it has had time to grow deeper — which is exactly what paying attention to a mole is for.

How a mole is actually confirmed — and what to do now

There is no way to confirm melanoma from a photo, an app, or a description. The diagnosis is made by removing the spot, or a full-thickness sample of it, and examining the tissue under a microscope 6Ref 6Swetter SM, Tsao H, Bichakjian CK, et al. (2019).Guidelines of care for the management of primary cutaneous melanoma.Melanoma is diagnosed by biopsy (excisional/full-thickness preferred), and tumor thickness guides subsequent surgical management and staging workup.. So the honest answer to 'how do I know if my mole is melanoma' is that you don't know from looking — and neither does anyone else, however experienced.

What you can do is act on what you see. Photograph the mole in good light with a ruler for scale, note the date, and have a changing or worrying mole evaluated. Bring the photos to the visit; a dated series showing growth or a new color is genuinely useful to a clinician. A mole that is new, clearly changing, itching, bleeding, or not healing is a symptom to have looked at, not something to monitor indefinitely.

If melanoma is confirmed, the thickness measured at biopsy guides what follows, from wider removal to checking nearby lymph nodes 6Ref 6Swetter SM, Tsao H, Bichakjian CK, et al. (2019).Guidelines of care for the management of primary cutaneous melanoma.Melanoma is diagnosed by biopsy (excisional/full-thickness preferred), and tumor thickness guides subsequent surgical management and staging workup.. But the first move belongs to you: notice the change, document it, and get it seen. This page is a set of criteria for deciding a mole is worth checking — never a way to talk yourself out of one.

If a spot is biopsied, the procedure is usually quick and done under local anesthesia in the office; the sample goes to a pathologist, and results take a few days. A benign result ends the story. A melanoma result starts a plan built around the tumor's thickness — sometimes a wider removal, sometimes checking a nearby lymph node — where how deep it reaches and how far it has spread guide what follows 6Ref 6Swetter SM, Tsao H, Bichakjian CK, et al. (2019).Guidelines of care for the management of primary cutaneous melanoma.Melanoma is diagnosed by biopsy (excisional/full-thickness preferred), and tumor thickness guides subsequent surgical management and staging workup..