Melanoma typically appears as an unusual mole or spot with uneven color, irregular borders, and an asymmetrical shape. It can range from flat and subtle to raised and firm, and it doesn’t always look the way people expect. Some melanomas are dark brown or black, but others are pink, red, or even skin-colored. Knowing what to look for across the different forms this cancer takes is the best way to catch it early.
The ABCDE Rule
The most widely used framework for spotting a suspicious mole is the ABCDE checklist, developed by dermatologists and endorsed by the National Cancer Institute:
- Asymmetry: One half of the mole doesn’t match the other. If you drew a line through the center, the two sides would look different in shape or color.
- Border: The edges are ragged, notched, or blurred rather than smooth and well-defined. Pigment may seem to spread or fade into the surrounding skin.
- Color: Instead of one uniform shade, you see a mix of browns, tans, and blacks, sometimes with patches of white, gray, red, pink, or blue within the same spot.
- Diameter: Most melanomas are larger than 6 millimeters across (roughly the size of a pencil eraser) by the time they’re noticed, though they can be smaller.
- Evolving: The mole is changing. Any shift in size, shape, color, or texture over weeks or months is a red flag, especially if it starts itching, bleeding, or crusting.
Not every melanoma will check all five boxes, and some benign moles may hit one or two criteria. The more features a spot displays, the more reason to have it evaluated.
The Ugly Duckling Sign
Beyond examining a single mole, one of the most effective ways to spot melanoma is to compare it against the other moles on your body. Most people have a personal “pattern” to their moles: similar size, similar color, similar shape. A melanoma often stands out as the one mole that looks nothing like the rest. Dermatologists call this the ugly duckling sign, and research published in JAMA Dermatology found that every melanoma in the study was identified as an ugly duckling, while using this comparison approach reduced unnecessary biopsies nearly sevenfold. If one spot on your body looks obviously different from its neighbors, that alone is worth paying attention to.
Flat Melanoma on Sun-Damaged Skin
The most common type of melanoma, called superficial spreading melanoma, starts as a flat or barely raised spot that grows outward across the skin’s surface before it pushes deeper. Early on, it tends to show an irregular pigment network with three or more colors and noticeable asymmetry. It can appear anywhere on the body but is frequently found on the trunk in men and the legs in women.
A related form, lentigo maligna, develops almost exclusively on chronically sun-damaged skin, particularly the face, ears, and forearms of older adults. It begins as a subtle, flat patch with an uneven mix of light brown, dark brown, tan, pink, or black. Because it starts so faintly and grows slowly over years, it’s easy to dismiss as a sun spot or age spot. If a flat brown patch on your face is gradually expanding or developing darker areas within it, that warrants a closer look.
Raised, Dome-Shaped Melanoma
Nodular melanoma looks and behaves quite differently from the flat varieties. It grows vertically, pushing down into deeper skin layers rather than spreading outward, which makes it more aggressive. On the surface, it appears as a firm, dome-shaped bump that can be black, blue-black, brown, red, pink, or even the same color as your surrounding skin. The texture may be smooth, crusty, or rough (sometimes compared to cauliflower). It often resembles a blood blister that doesn’t resolve. Because most of the growth happens beneath the surface, like an iceberg, nodular melanoma can be deceptively small on top while already significant underneath. It typically develops over weeks to months rather than years, so a new, firm bump that appeared recently and doesn’t go away deserves prompt attention.
Melanoma on Palms, Soles, and Under Nails
Melanoma on the palms of the hands, soles of the feet, or under a fingernail or toenail is called acral melanoma. It’s the most common type of melanoma in people with darker skin tones, and it’s easy to miss because people don’t think to check these areas.
On palms and soles, it starts as a flat patch with uneven light-to-dark-brown pigment. The edges tend to follow the natural skin lines in an angular pattern. One useful clue: benign dark spots on the palms and soles tend to have pigment concentrated in the grooves (furrows) of the skin, while melanoma pigment shows up on the ridges. As the lesion progresses, it can become raised and shift to a darker blue-black color. Any spot on the palm or sole larger than about 7 millimeters should be evaluated.
Under a nail, melanoma usually shows up as a brown or black vertical streak running the length of the nail, typically around 3 millimeters wide with blurred edges. It most commonly affects the thumb or big toe. The streak may widen over time, and pigment can spread onto the surrounding skin at the base of the nail.
Pink and Skin-Colored Melanoma
Perhaps the most dangerous-looking melanoma is the one that doesn’t look dangerous at all. Amelanotic melanoma produces little to no pigment, meaning it can appear pink, red, or the same color as your skin. It may look like a persistent pimple, a small sore that won’t heal, or a shiny bump. Because it lacks the dark coloring people associate with melanoma, it’s frequently misdiagnosed. In one study, roughly 35% of misidentified amelanotic melanomas were initially thought to be a different, less serious type of skin growth. Others were mistaken for eczema, infections, or scars. A pink or red bump or patch that persists for more than a few weeks, especially if it bleeds, crusts, or grows, is worth having checked even though it doesn’t fit the typical melanoma image.
How Melanoma Differs From Common Skin Growths
One of the most frequent sources of confusion is a seborrheic keratosis, a harmless growth that can be dark brown or black and therefore alarming. The key differences: seborrheic keratoses look like they’ve been stuck or pasted onto the skin’s surface, have a waxy or scaly texture, are round or oval with well-defined edges, and tend to appear in groups. They typically stay the same size and shape over time. Melanoma, by contrast, has a smoother surface, irregular or blurred borders, color variation within the lesion, and changes over time.
Other spots people commonly confuse with melanoma include cherry angiomas (bright red, perfectly round, and uniform) and dermatofibromas (firm, small, usually one consistent color). The distinguishing thread across all of these comparisons is the same: melanoma changes, has uneven features, and doesn’t look uniform.
Signs a Spot Is Changing
Evolution is often the single most important warning sign, because it applies even when a spot doesn’t clearly meet the other ABCDE criteria. Changes to watch for include a mole that’s getting bigger, developing new colors, or shifting in shape. Physical symptoms matter too: new itching, tenderness, bleeding, oozing, or crusting on a mole that was previously quiet. A spot that develops a raised area within a previously flat surface is also concerning, as this can signal deeper invasion. Taking photos of questionable moles every few months gives you a reliable way to track whether something is truly changing or just looks different depending on the lighting.