Melanoma moles typically look uneven in shape, color, or border compared to normal moles. Most are larger than 6 millimeters (about the size of a pencil eraser), though some start smaller. The key difference between a melanoma and a harmless mole is that melanomas break the rules of symmetry, color uniformity, and stable size that ordinary moles follow. Knowing what to look for across different types of melanoma can help you catch changes early, when treatment is most effective.
The ABCDE Rule for Spotting Melanoma
The most widely used framework for identifying melanoma is the ABCDE rule, developed by the National Cancer Institute. Each letter describes a visual feature to watch for:
- Asymmetry: If you drew a line through the middle of the mole, one half wouldn’t match the other. Normal moles are roughly symmetrical.
- Border irregularity: The edges look ragged, notched, or blurred rather than smooth and well-defined. Pigment may visibly spread into the surrounding skin.
- Color variation: Instead of one uniform shade, you see a mix of brown, tan, and black, sometimes with patches of white, gray, red, pink, or blue within the same spot.
- Diameter: Most melanomas are wider than 6 millimeters at diagnosis, though they can be smaller when first developing.
- Evolving: The mole has changed in size, shape, or color over the past few weeks or months. Any noticeable change is worth attention.
No single feature confirms melanoma on its own. A mole with two or three of these features is more concerning than one with just a slightly irregular border. That said, evolution is the most important signal. A mole that is clearly changing deserves a closer look regardless of whether it checks the other boxes.
How Melanoma Differs From Normal and Atypical Moles
Common moles are usually smaller than 5 millimeters, evenly colored in pink, tan, or brown, and round or oval with a clean edge. They may start flat and become slightly raised over time, but they maintain a smooth, uniform surface. Most adults have between 10 and 40 of them, and they look similar to each other.
Atypical moles (sometimes called dysplastic nevi) sit in a middle ground that can cause confusion. They’re often wider than 5 millimeters and can have a mix of tan, brown, and pink shades. Their edges may be irregular and fade into surrounding skin, and they sometimes have a raised center with a flat rim, giving them what dermatologists call a “fried egg” appearance. Atypical moles can look alarming, but they’re benign.
Melanoma goes further. The color variation is more dramatic, incorporating shades of black and blue alongside brown and tan. The surface may break down and look scraped, become hard or lumpy, or start to ooze or bleed. Where an atypical mole may have a slightly scaly or pebbly texture, a melanoma’s surface can look damaged or ulcerated. And critically, melanomas change over weeks or months, while atypical moles tend to stay stable once they’ve formed.
The Ugly Duckling Sign
Beyond the ABCDE rule, there’s a simpler approach that works especially well during self-checks. The “ugly duckling” sign means looking for the mole that doesn’t match the others. Most of your moles share a general family resemblance in size, shape, and color. If one mole stands out as clearly different from the rest, that outlier deserves closer attention, even if it doesn’t perfectly fit the ABCDE criteria.
Nodular Melanoma: The One That Doesn’t Look Flat
Not all melanomas spread outward across the skin’s surface first. Nodular melanoma grows downward quickly, appearing as a firm, dome-shaped bump rather than a flat, spreading patch. It can be dark brown or black, but it sometimes looks like a blood blister, appearing red, pink, or even skin-colored. This type develops fast, often over just several weeks, which makes it more dangerous than slower-growing forms.
Because it doesn’t follow the typical flat, spreading pattern, nodular melanoma can slip past the ABCDE rule. A different set of warning signs applies: elevated (raised above the skin), firm to the touch, and growing. If you notice a new bump on your skin that is firm, dome-shaped, and getting bigger over weeks, that’s enough reason to have it checked.
Melanoma Without Dark Color
About 5 percent of melanomas are amelanotic, meaning they lack the dark pigment most people associate with skin cancer. These appear as pink or red spots on the skin rather than brown or black ones. Because they don’t look like what people expect melanoma to look like, they’re frequently mistaken for harmless skin irritations, pimples, or scars, and tend to be diagnosed at a later stage as a result.
If you have a pink or reddish spot that persists for weeks, doesn’t heal, or slowly grows, it’s worth having evaluated. This is especially true if the spot is firm, slightly raised, or has an irregular outline.
Melanoma on Palms, Soles, and Under Nails
Acral lentiginous melanoma appears in places people rarely think to check: the palms of the hands, soles of the feet, and under fingernails or toenails. On the palms or soles, it typically looks like an unevenly pigmented black or brown spot that stands out from the surrounding skin and grows over time.
Under a nail, this type of melanoma shows up as a dark streak or pigmented band running from the cuticle toward the tip. Not every dark line under a nail is melanoma (minor injuries and normal pigmentation can cause them too), but a new streak that widens, darkens, or extends onto the skin around the nail is a red flag. This type of melanoma is more common in people with darker skin tones, and it accounts for a larger proportion of melanoma diagnoses in Black, Hispanic, and Asian populations.
Slow-Growing Melanoma on Sun-Damaged Skin
Lentigo maligna is a form of melanoma that develops on chronically sun-damaged skin, most often on the face and neck. It’s diagnosed most frequently in people between 60 and 80 years old. In its early stages, it looks like an ordinary age spot or freckle, which is exactly why it’s easy to ignore.
Over time, though, it grows larger (often reaching several centimeters), develops irregular borders, and takes on uneven coloring that shifts between light brown, dark brown, pink, and sometimes white. The progression is slow, sometimes unfolding over years or even decades, but that gradual change is itself a warning sign. If a facial brown spot is slowly expanding, changing shape, or developing new colors, it’s not behaving like a simple sun spot.
Signs that lentigo maligna may be turning invasive include thickening within part of the patch, the appearance of blue or black coloring, ulceration or bleeding, and itching or stinging sensations.
What Melanoma Can Be Confused With
Seborrheic keratoses are one of the most common melanoma lookalikes. These are waxy, stuck-on-looking growths that appear with age, and they can be dark brown or black, making them look suspicious. The key difference is their texture: seborrheic keratoses often have tiny white cysts or pore-like openings visible on their surface, and they look like they’ve been pasted onto the skin rather than growing from within it. If a dark lesion has those waxy, cyst-filled surface features and no other concerning characteristics, it’s more likely benign.
Still, visual similarity between these growths and melanoma can fool even experienced eyes. Any lesion that is changing, bleeding, or looks different from your other spots warrants a professional evaluation. A dermatologist can use magnification tools to examine the internal structure of a spot in ways that aren’t possible with the naked eye, catching patterns that confirm or rule out melanoma with much greater accuracy than a visual self-check alone.