A spot is more likely to be skin cancer if it looks different from your other spots, has changed recently, or won’t heal. No photo or checklist can replace a biopsy, which is the only way to confirm skin cancer. But certain visual clues can help you decide whether a spot deserves a closer look from a dermatologist.
Skin cancer takes three main forms, and each one looks different. Knowing what to watch for across all three gives you the best chance of catching something early.
Warning Signs of Melanoma
Melanoma is the most dangerous form of skin cancer, but it’s also the one with the clearest visual red flags. The National Cancer Institute uses five features, known as the ABCDE rule, to describe early melanoma:
- Asymmetry: One half of the spot doesn’t match the other half.
- Border irregularity: The edges are ragged, notched, or blurred rather than smooth. Pigment may spread into the surrounding skin.
- Color variation: The spot contains uneven shades of brown, black, or tan. You may also see patches of white, gray, red, pink, or blue within the same lesion.
- Diameter: Most melanomas are larger than about 6 millimeters (roughly the size of a pencil eraser), though they can be smaller.
- Evolving: The spot has changed in size, shape, or color over the past few weeks or months.
Of these five, “evolving” is often the most useful in practice. A mole that has looked the same for years is far less concerning than one that’s shifted in any way recently.
The Ugly Duckling Test
Another approach is simpler: look for the mole that doesn’t match the rest. Most people’s moles share a general “family resemblance” in size, shape, and color. If one mole stands out from all the others, that outlier deserves attention. Dermatologists call this the ugly duckling sign, and it can flag melanomas that don’t tick every box on the ABCDE list.
What Basal Cell Carcinoma Looks Like
Basal cell carcinoma is the most common skin cancer, and it often looks surprisingly subtle. The classic form is a small, slightly transparent or pearly bump. On lighter skin, it typically appears skin-colored or pink with a waxy, translucent quality. You may notice tiny blood vessels running through it. On brown or Black skin, it often shows up as a brown, glossy black, or tan bump with a rolled border.
Not all basal cell carcinomas look like bumps, though. Some appear as flat, scaly patches with or without a raised edge. Others resemble a white, waxy, scarlike area with no clearly defined border. A key behavior to watch for: the spot bleeds easily, scabs over, and then reopens. A “pimple” or small wound that keeps cycling through bleeding and crusting without ever fully healing is a classic presentation.
What Squamous Cell Carcinoma Looks Like
Squamous cell carcinoma tends to look rougher and more textured than basal cell. Common forms include a firm bump or nodule (which can be skin-colored, pink, red, brown, or black depending on skin tone), a flat sore topped with a scaly crust, or a rough, scaly patch on the lip that may break open into a sore. It can also appear as a raised, wartlike growth.
One telltale pattern: a new sore or raised area that develops on top of an old scar. If you have a sore or scab that hasn’t healed in about two months, that’s a strong reason to get it checked.
Pre-Cancerous Spots Worth Watching
Actinic keratoses are rough, dry, scaly patches that develop on sun-exposed skin. They’re usually small (under an inch across), flat or slightly raised, and can be pink, red, or brown. Some feel like sandpaper before you can even see them clearly. They may itch, burn, bleed, or crust over.
These patches aren’t cancer yet, but about 5% to 10% of them progress to squamous cell carcinoma if left untreated. A dermatologist can remove them quickly, which is why they’re worth identifying early rather than ignoring.
Harmless Spots That Mimic Cancer
Not every dark or unusual spot is dangerous. Two common lookalikes cause unnecessary worry:
Seborrheic keratoses are waxy, raised growths that look like they’re sitting on top of the skin, almost like a barnacle. They can range from pale brown to orange to black and vary in size. They have a well-defined edge and a stuck-on appearance. Most people develop at least one or two by age 60. They’re completely harmless.
Normal moles are typically round or oval, evenly colored (brown, black, or skin-toned), and have smooth, well-defined borders. Having many moles can run in families or result from childhood sun exposure. A mole that has stayed the same size, shape, and color for years is almost always benign. The moment it starts changing is when it warrants a professional look.
Skin Cancer on Darker Skin
Skin cancer looks different on brown and Black skin, and it often appears in locations people don’t think to check. The most common melanoma in people with dark skin is acral lentiginous melanoma, which develops on the palms, soles of the feet, fingers, toes, and under the nails. It can look like a dark patch on your palm or the bottom of your foot, or a dark band running lengthwise under a fingernail or toenail.
Squamous cell carcinoma on darker skin can appear as a firm bump or flat sore that matches the surrounding skin tone, or shows as pink, red, black, or brown. Basal cell carcinoma often presents as a brown or glossy black bump with a rolled border. Because these cancers can blend with the natural skin color, changes over time are especially important to track. Watch for any new growth, a patch that darkens or changes color, a sore that won’t heal, or a dark band developing under a nail.
How to Do a Self-Exam
The American Academy of Dermatology recommends a systematic head-to-toe check. You’ll need a full-length mirror and a hand mirror. Start by examining your body front and back in the full-length mirror, then raise your arms and check both sides. Bend your elbows and look at your forearms, underarms, fingernails, and palms.
Next, 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, your scalp (part your hair to look closely), your back, and your buttocks. The whole process takes about ten minutes, and doing it regularly helps you notice changes, which is the single most important thing you’re looking for.
What Happens If a Spot Looks Suspicious
The only way to know for certain whether a spot is cancerous is a biopsy, where a small sample of skin is removed and examined under a microscope. The type of biopsy depends on what your doctor suspects.
For spots that might be basal or squamous cell carcinoma, a shave biopsy (removing a thin layer from the surface with a blade) or a punch biopsy (using a small circular tool to take a deeper, pencil-eraser-sized sample) is common. For suspected melanoma, doctors typically do an excisional biopsy, removing the entire suspicious area with a scalpel and closing the site with stitches. This ensures they capture the full depth of the lesion.
All three types are done with local numbing and are outpatient procedures. Results usually come back within one to two weeks. If the biopsy confirms cancer, the type and depth determine the next steps, but catching it at the stage where you noticed something “off” about a spot is exactly when treatment works best.