When to get a mole checked: ABCDE signs and screening

An adult body carries somewhere between ten and forty moles on average, and the overwhelming majority of them will sit there unchanged for a lifetime. That is what makes the question difficult. The problem is never whether a mole exists; it is whether one particular spot is behaving differently from the others and differently from how it behaved last summer. Skin examines easily and forgets completely, which is why the useful signal is almost always change rather than appearance, and why a spot that looks unremarkable in isolation can still be the one that warrants an appointment.

🔍 What does the ABCDE rule actually check for?#

The ABCDE rule is a five-point checklist for deciding whether a pigmented spot deserves professional assessment: asymmetry, border irregularity, colour variation, diameter greater than about six millimetres, and evolution over time. It was published as ABCD in 1985 by a dermatology group at New York University in CA: A Cancer Journal for Clinicians, and the fifth letter for evolving was added in a 2004 paper in JAMA that revisited the original criteria. It is a triage instrument built for people without training, not a diagnostic test, and it was designed to produce appointments rather than answers.

Each letter describes a specific departure from how ordinary moles are built. A common benign mole tends to be roughly symmetrical, with an edge the eye can trace without interruption and a single shade of brown or tan spread evenly across it. Melanoma arises from melanocytes growing without the usual constraints, so the resulting lesion often expands faster in one direction than another, blurs at the edge, and produces two or three shades in the same spot.

The checklist has a known blind spot, and knowing it matters more than memorising the letters. Nodular melanoma, a faster-growing subtype that grows downward more than outward, is frequently symmetrical, evenly coloured, well-defined at the edge and smaller than six millimetres when it first appears, which means it can satisfy four of the five criteria and still be serious. Australian dermatology literature in the early 2000s proposed a supplementary checklist of E, F and G for this pattern: elevated, firm to the touch, and growing continuously over a period of about a month. A raised, firm bump that keeps enlarging is worth an appointment whether or not it is asymmetrical or darkly pigmented, and whether or not it is pigmented at all, since a proportion of nodular lesions are pink or skin-coloured.

📈 Which changes mean a spot should be seen sooner rather than later?#

Change is the criterion that outranks the rest, because it removes the need to judge a spot against an idealised description and replaces it with a comparison against the same spot two or three months earlier. A mole that has been the same size, shape and colour for a decade is providing evidence about itself. A mole that is visibly different from how it looked at the start of the year, or that has begun to itch, bleed, crust or feel tender without having been scratched or caught on clothing, is providing a different kind of evidence.

The ugly duckling sign is the second comparison worth making, and it works in a completely different way from a checklist. Described in Archives of Dermatology in 1998 by Grob and Bonerandi, it starts from the observation that an individual's moles tend to resemble one another, forming one or two recognisable family patterns. A spot that does not belong to any of those patterns, being noticeably darker, larger, pinker or simply odd next to its neighbours, is worth attention even when it satisfies none of the ABCDE criteria on its own. The method is comparative rather than absolute, which makes it unusually robust for people who have never seen a dermatology atlas.

The reason the interval matters is the relationship between how far melanoma has progressed at diagnosis and how treatable it is at that point. Melanoma identified while still confined to its original site behaves very differently from melanoma identified after it has reached lymph nodes or distant organs, and the gap between those situations is measured in months of delay rather than years.

Self-examination works best as a short, repeatable routine rather than an occasional anxious inspection, because the value of the exercise comes from comparing one month against the last. A phone camera helps, provided the photographs are taken in consistent light, from a consistent distance, and with a coin or ruler in frame so that size can be compared rather than estimated. Areas a person cannot see directly are the ones most often missed, and they are where a handheld mirror or a second pair of eyes changes the result.

🩺 What happens during a skin cancer screening appointment?#

A skin cancer screening is a visual examination of the skin, usually supported by dermoscopy, with a biopsy performed only if a specific lesion warrants laboratory assessment. There is no blood test for melanoma screening, and no imaging scan is involved for a routine skin check. The appointment is typically short, often fifteen to thirty minutes for a full examination, and most people leave without anything having been removed.

Dermoscopy is the step that separates a professional skin check from a careful look in a mirror. A dermatoscope is a handheld magnifier combined with polarised light that reduces surface reflection, allowing pigment structures within the upper layers of skin to be seen directly rather than inferred from the outline. Pattern features that are meaningless to the naked eye, such as an irregular pigment network, blue-white structures or an atypical vascular pattern, become visible, and multiple systematic reviews have found that dermoscopy in trained hands improves diagnostic accuracy compared with unaided visual inspection. The device touches the skin or hovers just above it, and the examination is painless.

If a biopsy is recommended, the method chosen is not arbitrary. Where melanoma is suspected, an excisional biopsy that removes the whole lesion with a narrow margin is generally preferred, because the depth of the lesion, measured as Breslow thickness, is the single most important factor in staging and cannot be measured reliably from a partial sample. Shave and punch techniques are used in other situations, including lesions that are large, awkwardly placed, or suspected of being a basal cell or squamous cell carcinoma rather than a melanoma. The procedure is performed under local anaesthetic, leaves a small wound closed with stitches or left to heal, and results usually return within roughly one to two weeks depending on the laboratory.

📋 Who needs a skin check, and how often?#

There is no single interval that applies to everyone, and the honest position is that expert bodies disagree about population-wide screening while agreeing about high-risk individuals. The US Preventive Services Task Force reviewed the evidence in 2023 and issued an I statement in JAMA, concluding that the evidence is insufficient to assess the balance of benefits and harms of visual skin cancer screening in asymptomatic adolescents and adults. That conclusion applies to screening people with no symptoms and no elevated risk. It says nothing about evaluating a spot that has changed, which is a diagnostic question rather than a screening one.

Risk in this context is a list of specific, well-characterised factors rather than a general impression. Carrying more than about fifty moles, having several atypical or irregular moles, a personal history of any skin cancer, a first-degree relative diagnosed with melanoma, skin that burns rather than tans, blistering sunburns particularly in childhood, past use of indoor tanning beds, long-term immunosuppression after an organ transplant, and a large congenital mole present from birth all raise the baseline. These factors compound rather than simply add, which is why most dermatology bodies grade their advice by profile instead of issuing one interval for everyone.

Lower risk is not the same as no risk, and this is where the most consequential misunderstanding sits. Melanoma is diagnosed less often in people with deeply pigmented skin, but it is more often diagnosed at a later stage in those same groups, which means the outcome gap runs in the opposite direction to the incidence gap. Part of the explanation is that the sites involved differ, and part is that the assumption of immunity delays presentation on both sides of the consultation. How melanin content changes the way skin responds to ultraviolet exposure and to clinical devices is set out in our guide to laser treatment and Fitzpatrick skin type.

👣 Why do palms, soles and nails deserve separate attention?#

Acral lentiginous melanoma arises on the palms, the soles and in the nail units, and it is the subtype most often missed because those sites are rarely inspected and because the lesions do not look like the pictures used to illustrate melanoma. It is not associated with sun exposure, which means the usual mental model of sun-damaged skin does not apply, and it accounts for a strikingly different share of melanoma diagnoses depending on population. Published case series place it in the low single-digit percentages of melanoma among people with fair skin, and at roughly half of melanoma diagnoses in East Asian populations, with higher proportions again reported in Black populations.

On a sole or a palm, the presentation is often a flat brown or black patch with uneven edges that expands slowly, and it is regularly mistaken for a bruise, a plantar wart, a callus or a fungal change. A sore on the sole that has not healed over a month or two, or a pigmented patch on weight-bearing skin that is changing shape, is worth showing to a dermatologist rather than treating as a mechanical problem. The delay in these cases usually comes from a plausible alternative explanation being available, since almost everything on a sole has an innocent explanation that fits.

Practical inspection of these sites takes about a minute and is easy to build into an existing routine. Both soles are checked sitting down with good light, the toes are separated, and each nail is examined without polish, which is the step most often skipped and the one that hides the finding. For anyone in Korea who wants a nail or sole lesion examined and would prefer to have the consultation in English, the practicalities of finding and booking that appointment are covered in our guide to English-speaking skin clinics in Korea.

✨ In short#

The useful question about a mole is not whether it looks unusual but whether it is behaving differently from the rest of the skin and from its own recent history. The ABCDE checklist gives five features worth noticing, with evolution carrying the most weight, and the ugly duckling comparison catches the spots that fit no checklist but stand apart from their neighbours. Neither tool diagnoses anything: both exist to decide whether an appointment is warranted. At that appointment, dermoscopy narrows the question and a biopsy settles it, with excisional biopsy preferred where melanoma is suspected because depth cannot be measured from a fragment. Routine screening of asymptomatic low-risk adults sits in an evidence gap that the US Preventive Services Task Force declined to resolve in 2023, while scheduled examination for people with many moles, a personal or family history, or immunosuppression is widely supported. Palms, soles and nails deserve their own minute of attention, particularly for people of East Asian or African descent, because the subtype that appears there is unrelated to sun exposure and is the one most often found late.