Melanoma typically appears as an unusual mole or dark spot on the skin that looks different from your other spots. It can be flat or raised, and it ranges in color from brown and black to pink, red, or even skin-toned. Most melanomas are larger than 6 millimeters wide (roughly the size of a pencil eraser), though they can start smaller. The key feature is that a melanoma stands out: it looks unlike your other moles, and it changes over time.
The ABCDE Rule for Spotting Melanoma
Dermatologists use a five-letter framework to describe the warning signs of early melanoma. These aren’t pass/fail criteria. A melanoma might show just one or two of these features, but the more that apply, the more suspicious the spot.
- Asymmetry. One half of the mole doesn’t match the other. Normal moles tend to be roughly symmetrical.
- Border irregularity. The edges are ragged, notched, or blurred rather than smooth and well-defined. Pigment may bleed into the surrounding skin.
- Color variation. Instead of one uniform shade, you see a mix of brown, tan, black, or unexpected colors like blue, gray, red, pink, or white within the same spot.
- Diameter. The spot is larger than 6 millimeters, about the width of a pencil eraser. Melanomas can be smaller than this, especially when caught early, but growth beyond that threshold is a red flag.
- Evolving. The mole has changed in size, shape, or color over the past weeks or months. Any new symptom, like itching, crusting, or bleeding, also counts.
How Different Types of Melanoma Look
Not all melanomas look alike. The most common type, superficial spreading melanoma, starts as a flat or slightly raised brown patch with irregular borders. You might see black, blue, or pink areas mixed in. These tend to appear on the trunk and head in men and on the lower legs in women.
Nodular melanoma looks quite different. Instead of spreading outward across the skin’s surface, it grows upward as a raised, firm bump. It’s often dark blue-black but can also be red or pink. The warning signs here follow a different shorthand: Elevated, Firm, and Growing. Nodular melanomas grow fast, with noticeable changes over days to weeks rather than months. That speed makes them more dangerous because they tend to be thicker by the time they’re noticed.
Acral lentiginous melanoma shows up in places most people don’t think to check: the palms of the hands, soles of the feet, and under fingernails or toenails. On the skin, it looks like an unevenly pigmented black or brown spot that doesn’t match the surrounding skin. Under a nail, it appears as a dark streak or band running from the cuticle to the tip. If pigment from a nail streak starts spreading into the skin around the nail, that discoloration (called the Hutchinson sign) is a strong warning. This type is more common in people with darker skin tones and is frequently diagnosed late because the location is easy to overlook.
Melanoma That Doesn’t Look Like Melanoma
About 5 percent of melanomas are amelanotic, meaning they lack the dark pigment most people associate with skin cancer. These appear as pink, red, or skin-colored spots and are easily confused with a pimple, scar, or irritated patch of skin. Because they don’t look “suspicious” in the traditional sense, amelanotic melanomas are often caught at a later stage. If you have a pink or reddish bump that doesn’t heal within a few weeks, or that slowly grows, it’s worth having it examined.
The Ugly Duckling Sign
Beyond the ABCDE criteria, one of the most practical ways to spot a problem is the “ugly duckling” approach. Most of your moles share a general family resemblance: similar size, shape, and color. A melanoma is the outlier. It might be one large, dark mole surrounded by smaller, lighter ones, or a single small, pale spot among a group of bigger, darker moles. The point isn’t what it looks like in isolation. It’s that it doesn’t match its neighbors. If one spot on your body looks like it doesn’t belong with the rest, pay attention.
How Melanoma Differs From Harmless Spots
Many people worry about seborrheic keratoses, those waxy, “stuck-on” looking growths that become more common with age. These can be dark enough to mimic melanoma at first glance, but there are reliable differences. Seborrheic keratoses tend to feel flat and waxy, with a surface that looks like a scab or a blob of candle wax pressed onto the skin. They’re usually painless and don’t change much once they appear. Melanoma, by contrast, has uneven color, irregular or jagged borders, and changes in size or shape over time. A seborrheic keratosis might look alarming, but it typically doesn’t evolve the way melanoma does.
Normal moles are also common sources of worry. A healthy mole is usually one uniform color, has smooth borders, and stays the same from month to month. It can be flat or raised, light or dark, but it’s stable. The moment a mole starts changing, developing new colors, growing, or becoming asymmetrical, it crosses into territory worth investigating.
What Changes as Melanoma Advances
Early melanoma is often thin, flat, and confined to the surface of the skin. At this stage (Stage I), the tumor is less than 1 millimeter deep. It may look like nothing more than an odd mole. As it progresses into Stage II, it grows deeper than 1 millimeter and may start to feel thicker or more raised. One of the more serious visual changes is ulceration, where the skin on top of the melanoma breaks down and may bleed, ooze, or crust over. Ulcerated melanomas carry a higher risk of spreading, even when they’re relatively small.
Tumors thicker than 4 millimeters carry a very high risk of spreading to other parts of the body. By this point, the spot is often visibly raised, firm, and may bleed with minor friction. The earlier you catch a melanoma, the thinner it tends to be, and thin melanomas have dramatically better outcomes.
How to Check Your Own Skin
A full skin self-check means looking at every surface, including your scalp, between your toes, the soles of your feet, and under your nails. Use a hand mirror or ask someone to help with hard-to-see areas like your back and the backs of your thighs. Taking smartphone photos of moles you want to track gives you a reliable way to detect subtle changes over time. When you see a dermatologist, bring those photos and notes about any spots that are new, changing, or just look off to you.
Pay special attention to spots in areas that get regular sun exposure: your face, ears, neck, arms, and legs. But don’t ignore hidden areas. Melanoma can develop anywhere skin exists, including places the sun never reaches.