Melanoma can look like an unusual mole, a dark streak under a nail, a bruise-like patch on your palm or sole, or even a pink bump with no dark color at all. There’s no single appearance, which is what makes it tricky to spot. But most melanomas share a handful of visual clues that set them apart from ordinary moles and freckles.
The ABCDE Rule for Spotting Melanoma
The most widely used framework for identifying a suspicious spot is the ABCDE rule, developed by the National Cancer Institute. Each letter describes one visual feature:
- Asymmetry. One half of the spot doesn’t match the other. A normal mole is usually roughly symmetrical.
- Border. The edges are ragged, notched, or blurred rather than smooth and well-defined. Pigment may spread into surrounding skin.
- Color. Multiple shades appear within the same spot. You might see combinations of black, brown, tan, white, gray, red, pink, or blue.
- Diameter. Most melanomas are larger than 6 millimeters across (about the size of a pencil eraser) at the time they’re noticed, though they can be smaller.
- Evolving. The spot has changed in size, shape, or color over the past few weeks or months. Any mole that’s visibly different from how it looked before deserves attention.
Not every melanoma checks all five boxes, and some benign moles may hit one or two. The rule works best as a screening tool: if a spot matches several of these features, it’s worth having a dermatologist look at it.
The “Ugly Duckling” Comparison
Another practical approach is simpler: look for the mole that doesn’t match the others. Most people’s moles tend to resemble each other in size, shape, and color. A spot that stands out from the rest, the ugly duckling, is worth a closer look. In a study comparing this method to the ABCDE rule, both approaches were equally good at catching melanoma, but the ugly duckling method was significantly better at correctly ruling out harmless moles. This means fewer false alarms and less unnecessary worry.
Flat, Spreading Melanoma
The most common type is superficial spreading melanoma. It starts as a flat or barely raised brown patch with irregular, asymmetric borders, often with scattered areas of black, blue, or pink within it. It tends to grow outward across the skin surface for months or even years before it begins pushing deeper. Because it stays flat for so long, people sometimes dismiss it as a new freckle or age spot. The key difference is that it keeps changing: slowly expanding, developing new colors, or forming an uneven border.
Raised, Dome-Shaped Melanoma
Nodular melanoma looks quite different. Instead of spreading sideways, it grows upward and downward like an iceberg, with most of the cancer below the skin surface. It appears as a firm, dome-shaped bump that may be black, blue-black, brown, red, pink, or even the same color as your surrounding skin. The texture can be smooth, crusty, or rough (sometimes described as cauliflower-like), and it feels hard or firm when you press on it. These are typically larger than 1 centimeter across and taller than 6 millimeters.
Nodular melanoma is one of the more dangerous types because it grows rapidly, often over just weeks or months. It can resemble a blood blister that doesn’t heal. If you notice a new, firm bump on your skin that keeps growing, don’t wait to see if it goes away on its own.
Pink or Skin-Colored Melanoma
Not all melanomas are dark. Amelanotic melanoma lacks the pigment that gives most melanomas their brown or black color. Instead, it appears as a pink or red spot on the skin. This makes it particularly easy to overlook or mistake for a pimple, bug bite, or minor irritation. The same ABCDE features (irregular borders, evolving size) still apply, but the color clue is missing, which often delays diagnosis.
Melanoma on Palms, Soles, and Nails
Acral lentiginous melanoma shows up in places people rarely think to check: the palms of the hands, the soles of the feet, and under fingernails or toenails. On the palm or sole, it looks like a dark brown or black patch that may resemble a bruise or stain. Unlike a bruise, it doesn’t fade. It grows larger over time.
Under a nail, this type of melanoma (called subungual melanoma) typically appears as a dark vertical streak running the length of the nail bed. It’s sometimes mistaken for blood under the nail or a fungal infection. As it progresses, it can cause the nail to crack or break. One important warning sign is the Hutchinson sign: darkened pigment that spreads from under the nail onto the surrounding skin of the fingertip or cuticle. If you see a dark band under a nail that’s getting wider or spreading to the skin around it, get it checked.
This is the most common form of melanoma in people with darker skin tones. Because melanoma awareness campaigns typically focus on sun-exposed areas and lighter skin, these spots are frequently missed or diagnosed late.
Melanoma on Sun-Damaged Skin
Lentigo maligna is a slow-growing type that develops on skin with years of sun exposure, most often on the face or neck. It starts as a flat, irregularly shaped patch that initially looks like a large freckle or age spot. Over time it expands, sometimes reaching several centimeters across, and develops uneven coloring with areas of light brown, dark brown, pink, red, or white. The surface stays smooth and flat for a long time, which makes it easy to ignore. Because it appears on the face, people often assume it’s just a sun spot.
How Melanoma Looks on Darker Skin
On darker skin, melanoma can appear as a dark or black bump that may look waxy or shiny. It can also show up as a patch of skin that’s a different color from the surrounding area and keeps getting darker. The palms, soles, fingers, toes, and nail beds are the most common locations, making regular self-checks of these areas especially important.
Key things to watch for include a dark band under a fingernail or toenail that starts to widen, a dark patch on your palm or sole that doesn’t go away, or any area of skin that changes color and persists for more than a month.
What Melanoma Can Be Confused With
Several harmless skin growths can mimic melanoma’s appearance. Spitz nevi are pink-red, well-defined bumps most common in children and young adults that were once actually called “juvenile melanoma” before doctors recognized they were benign. Blue nevi are deeply pigmented, dark blue-black spots caused by melanocytes sitting deep in the skin. Atypical (dysplastic) nevi are moles with slightly irregular borders or uneven color that look suspicious but aren’t cancerous. And on sun-exposed skin in older adults, atypical lentiginous nevi can closely resemble early melanoma.
The overlap between harmless and dangerous is real, which is why dermatologists use dermoscopy (a magnified, lit examination) and biopsies to tell them apart. You don’t need to diagnose yourself. You need to notice what’s changed or what doesn’t look right and bring it to someone who can.