Skin cancer doesn’t always look dramatic. It can show up as a small shiny bump, a scaly patch that won’t go away, or a mole that’s slowly changing shape. The three most common types, basal cell carcinoma, squamous cell carcinoma, and melanoma, each have distinct visual clues you can learn to spot. No self-check replaces a professional evaluation, but knowing what to look for puts you in a much better position to catch something early.
Signs of Melanoma: The ABCDE Rule
Melanoma is the most dangerous common skin cancer, but it’s also the one with the clearest self-screening framework. The National Cancer Institute uses the ABCDE rule to describe features of early melanoma:
- Asymmetry: One half of the mole doesn’t match the other. Normal moles are generally round or oval and roughly symmetrical.
- Border: The edges are ragged, notched, or blurred rather than smooth. The pigment may seem to spread into the surrounding skin.
- Color: Instead of one uniform shade of brown, you see a mix of colors: black, brown, tan, and sometimes white, gray, red, pink, or blue within the same spot.
- Diameter: Most melanomas are larger than 6 millimeters across (about the size of a pencil eraser) when diagnosed, though they can be smaller.
- Evolving: The mole has changed in size, shape, or color over the past few weeks or months. Any new symptom, like itching or bleeding, also counts.
A mole doesn’t need to check every box to be suspicious. Even one of these features, especially a mole that’s actively changing, is worth getting looked at.
The “Ugly Duckling” Trick
Beyond the ABCDE rule, there’s a simpler, more intuitive approach. Your moles tend to look like each other. They share a general size, shape, and color that’s unique to you. An “ugly duckling” is a mole that stands out from all the others, the one that doesn’t match the family.
This comparison method is especially useful if you have a lot of moles. Instead of analyzing each one in isolation, you scan for the outlier. A dark brown mole among a field of light tan ones, or a large irregular spot surrounded by small round ones, deserves closer attention. Skin cancer researchers use this concept as a practical detection tool, and it works well for home checks too.
What Basal Cell Carcinoma Looks Like
Basal cell carcinoma is the most common skin cancer. It grows slowly and rarely spreads to other parts of the body, but it can cause significant damage to surrounding tissue if left untreated. It often appears on sun-exposed areas like the face, ears, neck, and scalp.
On lighter skin, look for a bump that’s skin-colored or pink with a slightly translucent, pearly quality. You might be able to see tiny blood vessels on or near the surface. On darker skin tones, it often appears as a brown or glossy black bump with a rolled border. In both cases, the bump may bleed, scab over, and then seem to heal before opening up again.
Basal cell carcinoma doesn’t always look like a bump, though. It can also show up as a flat, scaly patch that slowly grows larger, or as a white, waxy, scar-like area with no clear border. The hallmark across all these forms: a change in the skin that doesn’t resolve on its own, particularly a sore that keeps coming back.
What Squamous Cell Carcinoma Looks Like
Squamous cell carcinoma is the second most common skin cancer. It typically appears as a flat sore with a scaly crust, or a raised, wart-like bump. On the lip, it may start as a rough, scaly patch that eventually becomes an open sore. These growths tend to feel firm and can bleed or crust repeatedly.
Like basal cell, squamous cell carcinoma favors sun-exposed skin, but it can appear in less obvious places too, including inside the mouth. The key pattern to notice is a rough, persistent spot that doesn’t heal within a few weeks. If you have a crusty patch or bump that keeps scabbing and returning, that’s a reason to get it evaluated.
Less Common Types Worth Knowing
Merkel cell carcinoma is rare but aggressive. It tends to grow fast and spread quickly. It usually appears as a painless bump on the skin that’s pink, purple, red-brown, or skin-colored. The bump grows rapidly and its two sides often don’t match. Because it’s uncommon, many people (and even some clinicians) don’t immediately recognize it. Any fast-growing, painless bump on the skin, especially on the face, head, or neck, warrants a prompt visit.
Places You’re Probably Not Checking
Most people focus their self-checks on sun-exposed areas like the arms, face, and chest. That’s reasonable, but skin cancer can develop in spots that rarely or never see the sun.
Melanoma can form under fingernails or toenails, where it may look like a dark streak running the length of the nail. It can appear on the soles of your feet, a particularly common site among Black Americans, and between your toes and fingers. The scalp, hidden by hair, is another frequently missed location. Melanoma can even develop on the genitals, under the breasts, and on the eyelids (sometimes only visible with the eyes closed). In rare cases, it forms inside the eye as a dark spot on the iris.
A thorough self-check means looking at all of these areas. Use a hand mirror for the back of your body, and ask a partner to check your scalp and other hard-to-see spots.
Normal Moles vs. Suspicious Spots
A normal mole is typically one solid color (usually brown), smaller than a pencil eraser, symmetrical, and has smooth, well-defined borders. Most people develop new moles into their 40s, so a new spot isn’t automatically dangerous. What matters is whether that spot looks different from your others, whether it’s changing, or whether it has irregular features.
Benign moles tend to stay stable over time. They grow slowly and proportionally, maintaining their shape and color. A mole that shifts in color, develops uneven borders, or suddenly starts itching or bleeding is acting differently. That behavior is what should prompt you to take the next step.
What Happens if Something Looks Off
If you spot something suspicious, a dermatologist will examine it visually, often with a dermatoscope (a handheld magnifying tool with its own light source). If the spot looks concerning, the next step is a biopsy, which means removing a small sample of skin to examine under a microscope.
There are a few types of biopsy. A shave biopsy scrapes the surface layers of skin and usually doesn’t require stitches. A punch biopsy uses a small circular tool to remove a deeper sample, and may need a stitch or two depending on the size. An excisional biopsy removes the entire suspicious area along with a border of healthy skin and typically requires stitches. The type used depends on what the spot looks like and how deep the concern goes. All are done with local numbing and are relatively quick.
Results usually come back within one to two weeks. If the biopsy confirms cancer, treatment options depend on the type and how early it was caught, which is exactly why spotting changes early matters so much.
Skin Cancer Apps: Helpful but Limited
Smartphone apps that use AI to analyze photos of moles have become widely available. A 2025 study in the EJC Skin Cancer journal tested one such app and found it correctly identified skin cancers about 82.5% of the time, with a specificity of about 77%. When a dermatologist reviewed the app’s flagged images remotely, specificity improved to nearly 87%, but sensitivity dropped to 75%.
In practical terms, these apps miss roughly one in four to one in five skin cancers. They’re a reasonable supplement if they encourage you to pay closer attention to your skin, but they’re not reliable enough to use as a substitute for professional evaluation. If your gut says something looks wrong, trust that over an app’s reassurance.
How to Do a Self-Check
Pick a consistent schedule, monthly works well, and examine your entire body in good lighting. Start with your face, ears, and neck. Move to your chest, torso, and arms, checking both the tops and undersides. Use a full-length mirror and a hand mirror together to see your back, buttocks, and the backs of your legs. Check your hands and feet carefully, including the palms, soles, nail beds, and the spaces between fingers and toes. Part your hair to examine your scalp, or have someone else do it.
Taking photos of moles on your phone gives you a reference point for comparison next month. Changes are much easier to spot when you have a side-by-side image from four weeks ago than when you’re relying on memory alone.