The average adult has many moles — often in the range of 10 to 40 — and the vast majority will never cause any problems. But melanoma, the most dangerous form of skin cancer, causes thousands of deaths in the United States each year, and it often starts in or near an existing mole or as a new spot on the skin. Knowing when to worry about a mole is one of the most valuable health skills you can develop, because melanoma caught early is highly treatable, with a five-year survival rate above 99% for localized disease, while survival drops sharply once it has spread, according to the National Cancer Institute. The difference often comes down to recognizing a warning sign and acting on it. This article is part of our medical conditions guide.
The ABCDE Rule for Evaluating Moles
Dermatologists developed the ABCDE framework to give people a practical tool for self-examination. It is not a diagnostic test, but it is a well-established way to identify moles that warrant professional evaluation. The American Academy of Dermatology promotes the ABCDEs as a public self-check.
A: Asymmetry
Normal moles are roughly symmetrical. If you drew a line through the center, both halves would look similar. A mole that is noticeably asymmetrical, where one half looks different from the other in shape, color, or texture, should be examined by a dermatologist. Melanomas are frequently asymmetrical because the cells grow at uneven rates.
B: Border
Benign moles typically have smooth, even borders that are clearly defined. Worrisome moles have borders that are irregular, ragged, notched, or blurred. The edges may appear scalloped or may fade gradually into the surrounding skin rather than ending crisply. Irregular borders are among the more consistently observed features of melanoma.
C: Color
Normal moles are usually a single shade of brown. A mole that contains multiple colors, such as different shades of brown, tan, black, red, white, or blue, is more suspicious. Color variation within a single mole suggests that different populations of cells are present, which can be a feature of malignancy. Any mole that appears very dark or contains areas of blue-black coloring deserves prompt evaluation.
D: Diameter
Moles larger than about 6 millimeters (roughly the size of a pencil eraser) are, on average, more likely to be melanoma than smaller ones. However, this guideline has important exceptions. Melanomas can be smaller than 6 mm when first detected, and many benign moles are larger. Diameter is best used in combination with the other ABCDE criteria rather than as a standalone indicator.
E: Evolving
This may be the single most important criterion. Any mole that is changing in size, shape, color, elevation, or any other feature should be evaluated. New symptoms arising in a mole, such as itching, bleeding, or crusting, are also significant. The Cleveland Clinic emphasizes that evolution — any noticeable change over weeks to months — is the feature that most often prompts a melanoma diagnosis.
Beyond ABCDE: The Ugly Duckling Sign
Most of a person’s moles share a general “family resemblance.” They tend to be similar in color, size, and shape. The ugly duckling sign refers to a mole that looks distinctly different from all the others on your body. This outlier mole may not meet any of the specific ABCDE criteria, but its uniqueness makes it worth a professional look.
Research indexed on PubMed has explored how the ugly duckling sign can improve melanoma detection when used alongside the ABCDE rule. It is particularly useful for identifying small melanomas that have not yet developed classic features and for people with many atypical moles whose individual lesions are difficult to assess using standard criteria.
Specific Changes That Should Prompt Prompt Evaluation
While gradual evolution is concerning, certain changes deserve prompt dermatologic assessment.
A mole that bleeds without being scratched or injured is a red flag; melanomas can develop fragile, abnormal blood vessels that bleed spontaneously. A mole that becomes persistently itchy without an obvious cause such as an insect bite or contact irritant deserves attention. A mole that develops a sore or ulceration that does not heal within a few weeks should be evaluated and may need a biopsy.
Rapid growth, where a mole noticeably increases in size over weeks to a few months, is one of the more alarming patterns. While some benign conditions can cause rapid mole growth, this pattern warrants prompt evaluation. The appearance of satellite lesions, small new spots clustered around an existing mole, can indicate local spread of melanoma and requires urgent assessment. For related skin cancer concerns, our article on symptoms of melanoma spread covers what to watch for after diagnosis, while our guide to Mohs surgery cost covers the financial side of skin cancer treatment.
Melanoma Can Appear Anywhere, in Any Skin Tone
An important and sometimes overlooked point: melanoma is not limited to sun-exposed skin, and it is not limited to people with fair skin. Melanoma can develop on the palms, the soles of the feet, between the toes, under fingernails or toenails (a dark streak or band under a nail can be a warning sign), and even on mucous membranes such as inside the mouth or the genital area. This is sometimes called acral or mucosal melanoma.
People with brown and Black skin can and do develop melanoma, and it is more likely to appear on the palms, soles, and nails. Because these areas are easy to overlook and because melanoma in skin of color is sometimes diagnosed later, awareness matters for everyone. Check the whole body, not just the areas that see the sun.
Types of Skin Cancer That Start as or Near Moles
Understanding the different types of skin cancer helps contextualize when to worry about a mole.
Melanoma is the most dangerous type. It accounts for a small share of skin cancers but causes the majority of skin cancer deaths. Melanoma can develop in a pre-existing mole or appear as a new dark spot, and it can occur anywhere on the body, including areas not regularly exposed to the sun.
Basal cell carcinoma, the most common skin cancer, typically appears as a pearly or waxy bump, a flat flesh-colored or brown scar-like lesion, or a sore that bleeds and scabs repeatedly. It rarely develops from a mole but can occur near one. Squamous cell carcinoma often presents as a firm red nodule, a flat lesion with a scaly or crusted surface, or a sore that heals and returns. According to the Mayo Clinic, both basal and squamous cell carcinomas are highly treatable when caught early but can become locally destructive or, less commonly, spread if neglected.
Risk Factors for Melanoma
Knowing your risk level helps you decide how vigilant to be with mole monitoring. Fair skin, light hair, and light eyes increase melanoma risk, though people with darker skin tones can and do develop melanoma. A history of sunburns, particularly blistering sunburns during childhood and adolescence, is a major risk factor, as is the use of indoor tanning beds. Having many common moles or any atypical (dysplastic) moles elevates risk.
A personal history of any type of skin cancer increases the likelihood of developing another. A family history of melanoma, especially in a first-degree relative, raises your risk. Immunosuppression from organ transplantation, certain conditions, or immunosuppressive medications also increases melanoma risk. The CDC notes that melanoma remains among the more common cancers, and that reducing ultraviolet exposure — from the sun and from tanning beds — is a key way to lower risk.
Sun Protection: Lowering Your Risk
You cannot change some risk factors, but you can reduce ultraviolet exposure. Dermatology and public-health organizations generally advise seeking shade during peak sun hours, wearing protective clothing and a wide-brimmed hat, using UV-blocking sunglasses, applying a broad-spectrum sunscreen of at least SPF 30 and reapplying as directed, and avoiding indoor tanning entirely. These habits help protect against melanoma and the more common skin cancers alike, while regular self-checks help you catch anything early.
How to Perform a Self-Examination
Monthly skin self-examinations are recommended by many dermatologists, particularly for people with elevated risk factors. The exam should cover your entire body, including areas you might overlook.
Start in a well-lit room with a full-length mirror and a hand mirror. Examine your face, ears, and scalp (use a comb or blow dryer to part hair). Check both sides of your hands, your forearms, upper arms, and armpits. Use the full-length mirror to examine your torso front and back. Check both legs, including the backs of the calves and thighs. Examine the soles of your feet, between your toes, and your toenails. Use the hand mirror to check the back of your neck, your scalp, your back, and your buttocks. Ask a partner or family member to help with hard-to-see areas.
Take photos of moles that concern you so you can track changes over time. Many smartphone apps exist for mole tracking, though none should substitute for professional evaluation of a suspicious lesion. The goal of self-examination is not self-diagnosis but early identification of changes that warrant dermatologic assessment.
When a Dermatologist Should Evaluate Your Mole
Schedule a dermatology appointment if any mole meets one or more ABCDE criteria, if a mole has changed in any noticeable way over recent weeks or months, if you have a mole that bleeds, itches, or develops a sore that will not heal, if you notice an ugly-duckling mole that looks different from all your others, if you see a new or changing dark streak under a nail, or if you have risk factors and have not had a professional skin exam in the past year.
Dermatologists use dermoscopy, a magnified examination of the skin surface, to evaluate suspicious moles with far greater accuracy than the naked eye. If a mole is suspicious, a biopsy is performed, typically in the office under local anesthesia, with results usually available within one to two weeks. Do not let worry keep you from getting a concerning mole checked — the evaluation is quick and low-risk, and an answer either way is reassuring.
Frequently Asked Questions
Can a mole become cancerous overnight?
No. Melanoma develops gradually over weeks to months, though it may seem sudden when you first notice a change. This is why regular self-examination is important: monthly checks help you catch changes when they are subtle rather than after they have become obvious.
Should I worry about a raised mole?
Raised moles are extremely common and usually benign. A mole that has been raised for years and has not changed is rarely concerning. However, a previously flat mole that becomes raised, or a raised mole that changes in any other way, should be evaluated. The key is always change over time.
Are new moles in adults dangerous?
New moles can appear normally into your 30s and sometimes 40s, but new pigmented spots appearing later in adulthood are less common and deserve more scrutiny. Any new mole in an adult that grows quickly, has irregular features, or looks different from your existing moles should be evaluated by a dermatologist.
Does a painful mole mean cancer?
Most melanomas are painless. Pain in a mole is more commonly caused by irritation, inflammation, or an underlying cyst. However, pain combined with other changes such as growth, color change, or bleeding warrants evaluation. Do not assume a painful mole is benign simply because it hurts, and do not assume a painless mole is safe simply because it does not.
Can I get melanoma if I have dark skin?
Yes. People of all skin tones can develop melanoma. In brown and Black skin it more often appears on the palms, soles, and under the nails, and it can be diagnosed later because these areas are easy to overlook. Everyone should check the whole body, including the hands, feet, and nails.
How often should I get a professional skin check?
Many dermatology organizations recommend regular professional skin examinations for people with elevated risk factors, often annually, while those at average risk should discuss screening frequency with their clinician. Regardless of risk level, any mole that concerns you should be evaluated without waiting for your next scheduled visit.
The Bottom Line
Most moles are harmless. The ones that matter are the ones that are changing. Use the ABCDE rule and the ugly-duckling sign during monthly self-examinations, remember that melanoma can appear anywhere and in any skin tone, and see a dermatologist promptly for any mole that meets these criteria or that simply worries you. A skin biopsy is a simple, low-risk procedure that provides a definitive answer. Given that early melanoma is highly curable while late-stage melanoma has a much poorer prognosis, the few minutes you spend examining your skin each month may be among the most valuable health habits you keep.
TL;DR
- Use the ABCDE rule — Asymmetry, Border, Color, Diameter, Evolving — to flag moles that need a dermatologist; “Evolving” (any change) matters most.
- The ugly-duckling sign (a mole unlike your others), plus itching, bleeding, or a sore that won’t heal, are additional warning signs.
- Melanoma can appear anywhere, including nails, palms, soles, and mucous membranes, and in people of all skin tones.
- Most moles are benign, but early melanoma is highly curable — see a dermatologist promptly for any concerning mole.
- Protect your skin from UV, and do monthly full-body self-checks.
This article is for general education only and is not medical advice or a substitute for evaluation by a qualified dermatologist. When in doubt about any mole, get it checked.
Sources
- American Academy of Dermatology (AAD) — ABCDEs of melanoma, self-exams, and sun protection (aad.org)
- Mayo Clinic — melanoma and skin cancer symptoms and causes (mayoclinic.org)
- National Cancer Institute — melanoma statistics and survival (cancer.gov)
- Cleveland Clinic — moles and melanoma patient information (clevelandclinic.org)
- Centers for Disease Control and Prevention (CDC) — skin cancer prevention and risk (cdc.gov)
- Skin Cancer Foundation — ugly-duckling sign and self-examination guidance (skincancer.org)