Skin cancer usually shows up as a visible change on your skin: a new spot, a mole that looks different than it used to, or a sore that refuses to heal. There’s no single sign that confirms it, but learning what to look for can help you catch something early, when treatment is simplest.
The ABCDE Rule for Melanoma
Melanoma is the most dangerous form of skin cancer, and it has a distinct set of visual warning signs. The National Cancer Institute uses the ABCDE framework to describe what early melanoma looks like:
- Asymmetry: One half of the mole doesn’t match the other.
- Border: The edges are ragged, notched, or blurred rather than smooth. Pigment may spread into the surrounding skin.
- Color: The color is uneven. You might see shades of black, brown, and tan mixed together, or areas of white, gray, red, pink, or blue.
- Diameter: Most melanomas are larger than 6 millimeters wide (about the size of a pencil eraser), though they can be smaller.
- Evolving: The mole has changed in size, shape, or color over the past few weeks or months.
Not every mole that meets one of these criteria is cancer, and not every melanoma will check all five boxes. But any mole showing multiple ABCDE features deserves a closer look from a dermatologist.
The Ugly Duckling Sign
If you have a lot of freckles or moles, the ABCDE rule can feel overwhelming. There’s a simpler way to scan your skin: look for the one spot that doesn’t match the rest. Maybe it’s more raised, has a different color, or has scabbed over. Dermatologists call this the “ugly duckling” sign. Just like in the childhood story, it’s the one that stands out from the group. That mismatch alone is enough reason to get it checked.
What Basal Cell Carcinoma Looks Like
Basal cell carcinoma is the most common type of skin cancer, and it looks quite different from melanoma. On lighter skin, it often appears as a shiny, translucent bump with a pearly white or pink tone. On brown and Black skin, the same bump tends to look brown or glossy black. You might notice tiny blood vessels running across the surface. These bumps can bleed, scab over, and then bleed again.
Other forms of basal cell carcinoma include flat, scaly patches that slowly expand over time, and white, waxy, scarlike areas without a clear border. Some lesions have a raised, translucent edge with dark spots inside. The key thread connecting all of these: they’re skin changes that persist and don’t resolve on their own.
What Squamous Cell Carcinoma Looks Like
Squamous cell carcinoma is the second most common skin cancer. It can show up as a firm bump (called a nodule) that may be pink, red, brown, or black depending on your skin tone. It can also appear as a flat sore with a scaly crust, a rough patch on the lip that becomes an open sore, or a new raised area developing on an old scar. Unlike basal cell carcinoma, squamous cell carcinoma sometimes appears inside the mouth or on the genitals.
Sores That Won’t Heal
One of the most overlooked warning signs of skin cancer is a sore that keeps coming back or simply never fully heals. A normal wound should show clear improvement within a few weeks. If a sore on your skin has persisted for a month or more without healing, that’s a red flag. This applies to sores that bleed, scab, seem to get better, and then open up again. Both basal cell and squamous cell carcinomas commonly present this way, and people often dismiss them as minor irritations for months before getting them evaluated.
Pre-Cancerous Spots to Watch
Actinic keratoses are rough, dry, scaly patches of skin caused by years of sun exposure. They’re usually less than an inch across and feel like sandpaper when you run your finger over them. Colors range from pink to red to brown, and they most commonly appear on the face, lips, ears, forearms, scalp, neck, and backs of the hands. Some develop a hard, wartlike surface. These patches aren’t cancer yet, but a small percentage of them progress to squamous cell carcinoma over time. Treating them early prevents that progression.
Skin Cancer on Darker Skin
Skin cancer is often described as something that primarily affects fair-skinned people, which leads to dangerous delays in diagnosis for people of color. Acral lentiginous melanoma is the most common type of melanoma in people with darker skin, and it shows up in places many people never think to check: the soles of the feet, the palms of the hands, and under the fingernails or toenails.
On the palms or soles, it looks like a black or brown discoloration that may resemble a bruise or stain. The key difference is that it grows over time rather than fading. Under the nails, it appears as dark vertical streaks running the length of the nail bed. As it progresses, it can cause the nail to crack or break. This type is sometimes mistaken for a fungal infection or an old injury, which is part of why it’s often diagnosed at a later stage.
Skin Cancer That Doesn’t Look Like a Mole
About 5 percent of melanomas are “amelanotic,” meaning they lack the dark pigment most people associate with skin cancer. These appear as pink or red spots on the skin rather than brown or black ones. Because they don’t look like what most people expect melanoma to look like, they’re frequently overlooked or confused with harmless skin irritations. This is one reason a monthly self-exam matters even if you’re watching your moles closely. You’re not just looking for dark spots. You’re looking for anything new, persistent, or changing.
How to Check Your Own Skin
The American Cancer Society recommends a monthly self-exam, ideally right after a bath or shower. You’ll need a well-lit room, a full-length mirror, and a handheld mirror for hard-to-see areas. Having a partner or close friend help with your back and scalp makes a big difference.
Work systematically so you don’t skip anything. Start with your face, ears, neck, chest, and belly. Women should lift the breasts to check the skin underneath. Move to your underarms, both sides of your arms, the tops and palms of your hands, between your fingers, and under your fingernails. Check the front of your thighs, shins, tops of your feet, between your toes, and under your toenails.
Then use the handheld mirror to examine the bottoms of your feet, calves, and backs of your thighs. Check your buttocks, genital area, lower and upper back, and the back of your neck and ears. Use a comb or hair dryer to part your hair and inspect your scalp. The whole process takes about 10 minutes once you’re used to it, and it becomes much faster after you know your baseline. You’re looking for anything new, anything that’s changed, and anything that fits the patterns described above.
What Happens at the Dermatologist
A dermatologist can evaluate suspicious spots visually and with a dermatoscope, a handheld magnifying tool with a built-in light. If something looks concerning, the next step is a biopsy, where a small sample of skin is removed and examined under a microscope. This is the only way to confirm whether a spot is cancerous.
The type of biopsy depends on what the doctor suspects. A shave biopsy removes a thin sample from the top layer of skin and is the most common approach. A punch biopsy uses a small round blade to take a deeper, pencil-eraser-sized sample, sometimes requiring a stitch or two. If melanoma is suspected, the doctor will typically do an excisional biopsy, removing the entire suspicious area with a small margin of normal skin around it. All three are done in the office with local numbing and take just a few minutes. Results usually come back within one to two weeks.