Melanoma typically appears as an unusual mole or dark spot that looks different from the other marks on your skin. It can show up as a flat, irregularly shaped patch, a raised bump, or even a streak under a fingernail. The key is knowing what specific features set melanoma apart from an ordinary mole, because catching it early makes an enormous difference in outcomes.
The ABCDE Rule for Spotting Melanoma
Most melanomas start as flat or slightly raised spots that share a set of visual warning signs. The National Cancer Institute uses the “ABCDE” framework to describe them:
- Asymmetry: One half of the spot doesn’t match the other. A normal mole is usually round or oval and roughly symmetrical.
- Border: The edges look ragged, notched, or blurred rather than smooth. Pigment may spread outward into the surrounding skin.
- Color: Instead of one uniform shade, the spot contains a mix of colors. You might see brown, tan, and black all in the same lesion, sometimes with patches of white, gray, red, pink, or blue.
- Diameter: Most melanomas are larger than 6 millimeters across, roughly the size of a pencil eraser. But they can be smaller, especially when caught early.
- Evolving: The spot has changed noticeably over the past few weeks or months, whether in size, shape, color, or texture.
Not every melanoma checks all five boxes, and not every mole that checks one box is melanoma. The most reliable single sign is evolution: any mole that is clearly changing deserves a closer look.
How a Normal Mole Looks Different
A typical benign mole is a small, evenly colored spot, usually tan, brown, or flesh-toned. Its border is smooth and well-defined, and both halves look like mirror images of each other. Most people have between 10 and 40 of these by adulthood, and they tend to stay the same size and shape for years.
Melanoma disrupts that predictability. Where a benign mole has organized, symmetrical clusters of pigment cells, a melanoma has irregular, disordered pigment cells that spread unevenly. In practical terms, this shows up on the surface as the ragged borders, mixed colors, and lopsided shapes described by the ABCDE criteria.
The “Ugly Duckling” Sign
Sometimes the easiest way to spot a suspicious mole isn’t analyzing a single spot in isolation. It’s noticing the one that doesn’t match the rest. If most of your moles are small, round, and brown, a larger, darker, or oddly shaped one stands out. That outlier is the “ugly duckling,” and it warrants attention even if it doesn’t clearly fit every ABCDE criterion.
Raised, Firm, and Fast-Growing Spots
Not all melanomas start flat. Nodular melanoma, one of the more aggressive forms, often appears as a raised, dome-shaped bump rather than a spreading patch. It can be dark brown, black, or even skin-colored, and it tends to grow quickly over just weeks to months.
Because nodular melanoma doesn’t always follow the ABCDE pattern, dermatologists use an additional set of warning signs called the EFG rule:
- Elevated: The lesion is raised above the surrounding skin.
- Firm: It feels solid to the touch, not soft or squishy.
- Growing: It is clearly increasing in size over a short period.
Any new bump on your skin that is firm, growing, and doesn’t heal or go away within a few weeks is worth having examined.
Pink and Red Melanomas Without Dark Pigment
About 5 percent of melanomas produce little or no pigment at all. These are called amelanotic melanomas, and they appear as pink, red, or skin-colored spots rather than the dark brown or black most people expect. They can look like a pimple, a scar, or an irritated patch of skin.
Because they lack the obvious dark color that triggers alarm, amelanotic melanomas are frequently overlooked or mistaken for harmless skin conditions. As a result, they tend to be diagnosed at a later stage compared to pigmented melanomas. If you have a pinkish or reddish spot that persists, doesn’t heal, or slowly grows, it’s not something to dismiss just because it isn’t dark.
Melanoma on Palms, Soles, and Under Nails
Melanoma can appear in places people rarely think to check. Acral lentiginous melanoma develops on the palms of the hands, soles of the feet, or under the nails. It occurs equally across all races and skin tones, but it accounts for the majority of melanoma cases in people of color, partly because other types of melanoma are less common on darker skin.
On the palms or soles, this type looks like a black or brown discoloration that might initially resemble a bruise or stain. The difference is that it doesn’t fade the way a bruise would. Instead, it gradually grows in size over time.
Under a fingernail or toenail, melanoma (called subungual melanoma) appears as a dark vertical streak running from the base of the nail to the tip. The streak is often irregular in color, with varying shades of blackish brown, and it typically starts narrower than 3 millimeters but widens over time, usually at the base of the nail first. As it progresses, pigment may spread beyond the nail itself and discolor the surrounding skin around the cuticle, a feature known as the Hutchinson sign. Advanced cases can cause the nail to crack or break. These streaks are sometimes mistaken for a fungal infection or dried blood under the nail, so any new dark line under a nail that doesn’t grow out with the nail deserves evaluation.
What to Actually Look For in Practice
Knowing the clinical criteria is useful, but in everyday life, melanoma detection comes down to a simple habit: familiarity with your own skin. When you know what your moles normally look like, you notice when one changes. A monthly self-check in good lighting, including the soles of your feet, between your toes, your scalp, and your nails, gives you a baseline to compare against.
The spots that matter most are the ones that are new and unusual, changing in any way, or clearly different from everything else on your body. Color mixing, irregular borders, and rapid growth are the highest-priority features. A mole that was stable for ten years and suddenly starts darkening on one side, bleeding, or itching is more concerning than a large mole that has looked the same your entire life. Melanoma is almost always curable when caught early and thin, so recognizing these visual patterns before a spot has time to deepen into the skin is what makes the difference.