Most moles are completely harmless, but certain visual clues can signal that something has changed or gone wrong. The key features to watch for fall into a well-established checklist: asymmetry, irregular borders, uneven color, increasing size, and any noticeable change over time. Catching a suspicious mole early matters enormously. Localized melanoma has a 97.6% five-year survival rate, while melanoma that has spread to distant parts of the body drops to 16.2%.
The ABCDE Checklist
This is the standard framework dermatologists use, and it works just as well at home. Each letter flags a specific trait worth examining.
- Asymmetry: If you drew a line through the middle of the mole, the two halves wouldn’t match. Normal moles tend to be roughly symmetrical.
- Border: The edges are ragged, notched, or blurred rather than smooth and well-defined. Pigment may spread or bleed into the surrounding skin.
- Color: Instead of one even shade, you see a mix of brown, tan, and black, or unexpected patches of white, gray, red, pink, or blue.
- Diameter: The mole is larger than about 6 millimeters, roughly the size of a pencil eraser. Melanomas can be smaller than this, but most exceed it.
- Evolving: The mole has changed in size, shape, color, or texture over the past few weeks or months. Any new symptom like itching, bleeding, or crusting also counts.
Not every suspicious mole will hit all five criteria. A mole that only meets one, particularly “evolving,” is still worth getting checked.
Normal Moles vs. Atypical Moles
A typical harmless mole is usually less than 5 millimeters wide, one even color throughout (pink, tan, brown, or matching your skin tone), and round or oval with a clear edge separating it from surrounding skin. It may start flat and eventually become a smooth raised bump, but its appearance stays consistent over time.
Atypical moles, sometimes called dysplastic nevi, look different in several ways. They’re often wider than 5 millimeters. Their color is a mix of tan, brown, red, or pink rather than one uniform shade. Their borders are irregular or notched and may fade gradually into the surrounding skin instead of having a crisp edge. The surface can feel rough, pebbly, or slightly scaly. Having atypical moles doesn’t mean you have cancer, but it does raise your overall risk and makes regular monitoring more important.
The Ugly Duckling Sign
The ABCDE criteria evaluate each mole on its own. The “ugly duckling” approach works differently: it compares a mole to all the other moles on your body. Most of your moles will share a general family resemblance in size, shape, and color. A mole that looks nothing like the rest, the one that stands out as odd, deserves closer attention even if it doesn’t obviously fail the ABCDE test. Dermatologists use this comparative method routinely because some melanomas don’t display classic warning features but still look distinctly “off” relative to a person’s other spots.
Moles That Don’t Look Like Moles
About 5% of melanomas are amelanotic, meaning they lack the dark pigment people typically associate with dangerous moles. These appear as pink, red, or skin-colored spots instead. Because they don’t look like the dark, irregular moles most people are watching for, amelanotic melanomas are often mistaken for pimples, bug bites, or scars and tend to be diagnosed at a later stage. If you have a pink or reddish bump that doesn’t heal, keeps growing, or feels firm, treat it with the same suspicion you’d give a dark mole.
Some aggressive melanomas also follow a different pattern called EFG: elevated above the skin surface, firm to the touch, and growing rapidly over days or weeks. These nodular melanomas can be dark or light in color, and their speed of growth is their most alarming feature.
Spots You Might Miss
Melanoma can develop in places most people never think to check. One important example is under your fingernails or toenails. Subungual melanoma typically appears as a dark vertical streak running from the bottom of the nail to the top, resembling a line drawn with a brown or black marker. The streak may start narrow (under 3 millimeters wide) but widen over time, especially near the cuticle. In some cases the nail splits, cracks, lifts away from the nail bed, or develops a nodule. Discoloration of the skin around the nail, known as Hutchinson sign, is a particularly important warning. Not all subungual melanomas produce a dark streak, though. Some cause nail deformity or a small growth without any visible color change.
The palms of your hands, soles of your feet, and spaces between your toes are other commonly overlooked areas. These sites are especially important for people with darker skin tones, in whom melanoma on the extremities is proportionally more common.
New Moles After 40
New moles can appear into your 40s and are not automatically dangerous. But the first sign of melanoma is often either a change in an existing mole or the appearance of a brand new spot. The older you are when a new mole shows up, the more attention it warrants. If you develop a new pigmented spot after your mid-40s, compare it to your other moles using the ugly duckling approach and run through the ABCDE checklist.
How to Do a Skin Self-Exam
A thorough self-check takes about 10 minutes and works best in a well-lit room with a full-length mirror and a hand mirror. The American Academy of Dermatology recommends a specific sequence so you don’t skip anything:
- Front and back: Stand before a full-length mirror. Look at your entire front, then turn and examine your back.
- Sides: Raise your arms and check your right and left sides.
- Arms and hands: Bend your elbows and look at your forearms, underarms, fingernails, and palms.
- Legs and feet: Check the backs of your legs, the spaces between your toes, your toenails, and the soles of your feet.
- Neck and scalp: Use a hand mirror to examine the back of your neck. Part your hair section by section to inspect your scalp.
- Back and buttocks: Use a hand mirror (or ask a partner) to check your back and buttocks.
Doing this once a month helps you learn what’s normal for your skin, which makes changes easier to spot. Taking photos of moles you want to track gives you a reference point for comparison.
Why Smartphone Apps Aren’t Reliable
Several apps claim to analyze photos of your moles and assess skin cancer risk. A systematic review published in The BMJ found poor and highly variable performance across these tools. No skin cancer risk assessment app has received FDA approval. Different apps gave conflicting recommendations for the same lesion, and image quality from consumer smartphone cameras in real-world conditions was a major limitation. The studies supporting these apps were small, used selective recruitment, and had high rates of unusable images. These apps include disclaimers that results are only a guide, but the bigger concern is that a false reassurance could delay someone from seeing a dermatologist. Your own eyes, using the ABCDE criteria and ugly duckling comparison, remain more dependable than any current app for flagging something that needs professional evaluation.