Skin cancer is the most common cancer, but it’s also one of the most visible. You can spot warning signs yourself by knowing what to look for. When melanoma is caught early, while still localized to the skin, the five-year survival rate is above 99%. Once it spreads to distant parts of the body, that number drops to 35%. The difference between those two outcomes often comes down to recognizing a suspicious spot before it progresses.
The ABCDE Rule for Melanoma
Melanoma is the most dangerous form of skin cancer, and dermatologists use a five-letter framework to describe its early warning signs. Each letter represents a feature to watch for in a mole or spot on your skin:
- Asymmetry: One half of the spot doesn’t match the other. Normal moles tend to be roughly symmetrical.
- Border irregularity: The edges are ragged, notched, or blurred rather than smooth. The pigment may seem to spread or fade into surrounding skin.
- Color variation: Instead of a single uniform shade, the spot contains a mix of brown, tan, black, red, white, blue, or gray.
- Diameter: Most melanomas are larger than about 6 millimeters (roughly the size of a pencil eraser) when diagnosed, though they can be smaller.
- Evolving: The spot has changed in size, shape, color, or behavior over the past few weeks or months. Any mole that looks different than it used to deserves attention.
A spot doesn’t need all five features to be suspicious. Even one or two of these characteristics, especially if the spot is evolving, is worth having a dermatologist evaluate.
The Ugly Duckling Sign
Most people’s moles share a general family resemblance. They tend to be similar in size, color, and shape. The “ugly duckling” sign works on a simple principle: if one spot on your body looks noticeably different from all the others around it, that outlier deserves a closer look. This approach, first described by dermatologists in 1998, was later shown to be a sensitive screening method for melanoma. You don’t need to memorize clinical criteria. Just scan your skin and ask yourself whether any single spot stands out as the odd one in the group.
What Basal Cell Carcinoma Looks Like
Basal cell carcinoma (BCC) is the most common skin cancer. It grows slowly and rarely spreads to other parts of the body, but it can cause significant local damage if ignored. On lighter skin, BCC often appears as a small, shiny, pinkish or pearly bump, sometimes with visible blood vessels running through it. It can also show up as a flat, pale or yellowish area that looks like a scar, or as a raised reddish patch that may itch.
One of the hallmark signs is a sore that won’t heal. It may ooze, crust over, seem to get better, and then open back up again. If you have a spot that has been going through that cycle for more than a month, that pattern alone is a red flag. On darker skin, BCCs share many of the same features (shiny surface, raised edges) but are often darker in color.
What Squamous Cell Carcinoma Looks Like
Squamous cell carcinoma (SCC) is the second most common skin cancer. It tends to appear on sun-exposed areas like the face, ears, neck, hands, and arms. The typical appearance is a rough, scaly red patch that may crust or bleed. It can also look like a raised lump, sometimes with a depressed center, or a wart-like growth that persists. Like BCC, squamous cell carcinoma can present as an open sore that doesn’t heal.
Both basal and squamous cell cancers can sometimes appear as flat areas that look only slightly different from normal skin. This is why routine self-checks matter. A subtle change you notice early can be easy to treat, while a spot you ignore for months may require more involved procedures.
Symptoms Beyond Appearance
Skin cancer isn’t always just a visual finding. Some spots itch, feel tender, or cause a burning sensation. A mole that starts bleeding on its own, without being scratched or bumped, is a warning sign. Crusting that keeps coming back, pain in a spot that previously felt normal, or a lesion that simply won’t heal are all signals worth acting on. Melanoma is usually painless early on but may itch or bleed as it progresses.
Skin Cancer on Darker Skin
Skin cancer is less common in people with darker skin tones, but it’s often diagnosed later, which makes it more dangerous. The most common form of melanoma in people with dark skin is acral lentiginous melanoma, and it shows up in places most people don’t think to check: the palms of the hands, the soles of the feet, under fingernails, and under toenails.
A dark streak or band under a nail that appears without any injury is a particularly important sign. If that dark band begins to widen or spread, that’s especially concerning. On the palms or soles, look for dark patches that are new or changing. It’s also worth watching any scar, particularly a burn scar, for changes in color or texture. Because these cancers occur in less sun-exposed areas, they’re easy to overlook during casual self-checks, which is why deliberately examining your hands, feet, and nails is essential.
How to Do a Full-Body Skin Check
You need two things: a full-length mirror and a hand mirror. The American Academy of Dermatology recommends a specific sequence to make sure you don’t skip areas:
- Stand in front of the full-length mirror and examine your body from the front and back. Raise your arms and check both sides.
- Bend your elbows and carefully look at your forearms, underarms, fingernails, and palms.
- Check the backs of your legs and feet, the spaces between your toes, your toenails, and the soles of your feet.
- Use the hand mirror to examine the back of your neck and your scalp. Part your hair in sections for a closer look.
- Use the hand mirror to check your back and buttocks.
The goal is to build a mental map of your skin so you notice when something changes. Some people find it helpful to take photos of moles they want to track, which makes it easier to spot subtle shifts in size or color over time. Doing this check once a month gives you the best chance of catching something early.
Atypical Moles vs. Melanoma
Atypical moles (sometimes called dysplastic nevi) can look alarming. They’re often larger than a pencil eraser, have irregular shapes with blurry edges, and may contain a mix of pink, red, tan, brown, and black. That description sounds a lot like the ABCDE criteria for melanoma, which is why these moles cause so much anxiety.
The key difference is stability. An atypical mole that has looked the same for years is far less concerning than one that has recently changed. Many people have atypical moles that never become cancerous. But having several of them does increase your overall risk, so if you have a lot of unusual-looking moles, regular skin checks (both at home and with a dermatologist) become more important. The “evolving” criterion is often the most useful tiebreaker: a mole that is actively growing, darkening, bleeding, or itching needs professional evaluation regardless of what it looks like.