Melanoma typically appears as an unusual mole or spot that looks different from the rest of your skin. It may be dark brown or black with uneven color, an irregular shape, or jagged borders. But melanoma doesn’t always look like what you’d expect. Some forms are pink, red, or even skin-colored, and others show up in places you’d never think to check, like under a toenail or on the sole of your foot.
The ABCDE Rule
The most widely used framework for spotting a suspicious spot is the ABCDE rule, developed by dermatologists to help people remember five warning signs:
- Asymmetry: One half of the mole doesn’t match the other. A normal mole is roughly symmetrical; melanoma tends not to be.
- Border: The edges are ragged, notched, or blurred rather than smooth. Pigment may spread into the surrounding skin.
- Color: The spot has uneven color. You might see shades of brown, black, and tan mixed together, or patches of white, gray, red, pink, or blue within the same lesion.
- Diameter: Most melanomas are larger than 6 millimeters across (about the size of a pencil eraser) by the time they’re caught, 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 noticeably different from how it looked before deserves attention.
The 6-millimeter threshold isn’t absolute. A study of biopsied lesions found that spots larger than 6 mm had a positive predictive value for melanoma of about 11.5%, compared to 2.6% for smaller ones. So size matters, but smaller melanomas exist and shouldn’t be dismissed just because they’re tiny.
The Ugly Duckling Sign
Beyond the ABCDE checklist, there’s a simpler concept worth knowing. The “ugly duckling” sign refers to any mole that looks distinctly different from the others on your body. Most of your moles share a family resemblance: similar color, size, and shape. If one stands out, looking nothing like the rest, that’s the one to have examined. This approach is especially useful for people with many moles, where evaluating each one against the ABCDE criteria would be overwhelming.
Nodular Melanoma
Not all melanomas spread outward across the skin’s surface first. Nodular melanoma grows vertically, pushing both above and below the skin like an iceberg. Most of the cancer lies beneath the surface. This makes it more dangerous because it can reach deeper tissue faster.
Visually, nodular melanoma appears as a firm, dome-shaped bump. It may be black, blue-black, brown, red, pink, or even the same color as your surrounding skin. The texture ranges from smooth to crusty to rough (sometimes described as cauliflower-like). These growths are generally larger than 1 centimeter across and are hard or firm to the touch. Some people initially mistake them for a blood blister that won’t go away. Because nodular melanoma doesn’t always follow the classic ABCDE pattern, the key warning signs are that it’s elevated, firm, and growing progressively over weeks.
Melanoma Without Dark Pigment
One of the trickiest forms is amelanotic melanoma, which lacks the dark coloring most people associate with skin cancer. These lesions are often described as skin-colored, but a significant number are pink or red. Early ones may appear as a flat, asymmetrical patch that’s uniformly pink or red, sometimes with faint tan, brown, or gray pigment around the edges. The borders can be either well-defined or blurry.
Because amelanotic melanomas often don’t trigger the classic ABCDE warning signs, they’re frequently diagnosed later. Some dermatologists use an expanded set of red flags for these: anything that’s red, raised, and recently changed. If you have a pinkish spot that you don’t remember having and it’s growing or changing, it’s worth getting checked even though it doesn’t look like a “typical” melanoma.
Melanoma on Hands, Feet, and Nails
Acral lentiginous melanoma develops on the palms of the hands, soles of the feet, or under the nails. It’s the most common type of melanoma in people with darker skin tones, and it’s often caught late because people don’t routinely examine these areas.
On the palm or sole, it starts as a black or brown discoloration that looks like a bruise or stain. Unlike a bruise, it doesn’t fade. Over time it grows in size and may become irregular in shape. Under a fingernail or toenail (called subungual melanoma), it typically appears as a dark vertical streak running the length of the nail bed. People often mistake it for a fungal infection or dried blood under the nail. As it progresses, the nail may crack or break.
Melanoma in the Eye
Melanoma can also develop inside the eye, where you can’t examine it yourself in a mirror. It forms in the cells that produce pigment within the eye’s structures. When there are visible signs, they include a growing dark spot on the iris (the colored part of the eye), a change in the shape of the pupil, or blurry vision in one eye. Some people notice flashes of light or floating specks in their vision, or a loss of peripheral (side) vision. Many eye melanomas produce no symptoms at all and are found during routine eye exams.
Melanoma vs. Harmless Skin Spots
Seborrheic keratoses are one of the most common benign growths that get confused with melanoma. These are flat, waxy, painless patches that can range from white to black. They often look like unusual scabs stuck to the skin and can appear anywhere on the body. The key differences: seborrheic keratoses tend to have a uniform, waxy texture and look like they’re “pasted on” the skin’s surface. Melanoma, by contrast, tends to have uneven coloring, irregular borders, and changes over time. A seborrheic keratosis may look alarming because of its dark color, but it typically doesn’t evolve the way melanoma does.
Age spots (solar lentigines) are another common source of worry. These are flat, evenly colored brown patches that appear on sun-exposed areas. They stay uniform in color and shape. If an age spot starts developing irregular borders, uneven pigment, or begins changing, that shift in behavior is what should prompt a closer look.
How to Check Your Own Skin
There’s no universal agreement on how often you need professional skin checks if you’re at average risk. The Skin Cancer Foundation recommends a full-body exam by a dermatologist once a year for everyone, while the U.S. Preventive Services Task Force says there isn’t enough evidence to recommend routine screening for people without symptoms or risk factors. If you have a personal or family history of melanoma, atypical moles, a weakened immune system, or a history of indoor tanning, more frequent professional exams are clearly warranted.
Regardless of your risk level, doing your own monthly skin check helps you notice changes early. Use a full-length mirror and a hand mirror to examine your back, scalp, and the backs of your legs. Check between your toes, the soles of your feet, your palms, and your nail beds. Look for anything new, anything that’s changed, and anything that looks different from your other spots. You know your skin better than anyone, and noticing a change is the single most useful thing you can do.