Skin cancer shows up in several distinct ways depending on the type, but the universal warning sign is a spot on your skin that looks different from everything around it or that changes over time. Learning what each type looks like gives you a real advantage: melanoma, the most dangerous form, has a survival rate above 99% when caught early and drops sharply when it’s not.
The ABCDE Rule for Melanoma
Melanoma is the skin cancer most people worry about, and for good reason. It can spread to other organs if it isn’t caught quickly. The National Cancer Institute uses five visual features, known as the ABCDE criteria, to help you spot it.
- Asymmetry: One half of the mole doesn’t match the other half. Normal moles tend to be 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, you see a mix of brown, tan, and black, sometimes with areas of white, gray, red, pink, or blue.
- Diameter: Most melanomas are larger than 6 millimeters across (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. Any noticeable change is worth attention.
Not every melanoma checks all five boxes. Some start as small, evenly colored spots that simply grow or darken. The “Evolving” criterion is arguably the most important single signal, because any mole that’s actively changing deserves a closer look.
Basal Cell Carcinoma: The Most Common Type
Basal cell carcinoma accounts for the majority of skin cancers. It grows slowly and rarely spreads to distant parts of the body, but it can damage surrounding tissue if ignored. It tends to appear on areas that get regular sun exposure, like the face, ears, and neck.
The classic sign is a shiny, pearly bump that looks pink, red, or white. In people with darker skin, the bump can appear tan, brown, or glossy black with a rolled border, making it easy to mistake for a regular mole. Another common presentation is an open sore that bleeds, oozes, or crusts over. The sore may seem to heal for a few days and then come back, persisting for weeks. A third form looks like a flat, scar-like area that’s white, yellow, or waxy, with shiny, taut skin and poorly defined borders. If you notice a patch of skin that looks like a scar but you don’t remember injuring the area, that’s worth investigating.
Squamous Cell Carcinoma: Scaly and Persistent
Squamous cell carcinoma is the second most common skin cancer. It appears most often on sun-exposed skin: the scalp, the backs of the hands, the ears, and the lips. It can also develop inside the mouth as a sore or rough patch on the lip that won’t heal.
The typical look is a firm nodule or a flat sore with a scaly crust. Some squamous cell cancers resemble warts. Color varies widely depending on skin tone. On lighter skin they’re often pink or red. On darker skin they can be brown, black, or the same color as the surrounding skin. One telling pattern is a new sore or raised area that develops on top of an old scar, because damaged skin is more vulnerable. If a rough, scaly patch persists for more than a few weeks or keeps returning after you think it’s healed, treat it as a warning sign.
Precancerous Spots to Watch
Actinic keratoses are rough, scaly patches caused by years of sun exposure. They aren’t cancer yet, but a small percentage of them progress to squamous cell carcinoma if left alone. Catching them early means simpler treatment.
These spots are often easier to feel than to see. Running your fingers over your skin, you might notice a patch that feels like sandpaper: dry, rough, or gritty. Some are tender, raw, or produce a prickling or burning sensation. Visually, they range from tiny specks to patches about an inch across, and they can be red, tan, pink, brown, silvery, or skin-colored. They sometimes develop a hard, horn-like bump on top. If you spend a lot of time outdoors and notice a rough patch that doesn’t smooth out on its own within a couple of weeks, it’s likely an actinic keratosis.
Signs on Darker Skin
Skin cancer in people with Black and brown skin often shows up in places that don’t get much sun, which means it’s easy to overlook. 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.
On the palm or sole of the foot, it can look like a dark, irregularly shaped patch. Under a fingernail or toenail, it typically appears as a dark vertical streak running from the base of the nail to the tip, as if someone drew a line with a brown or black marker. The streak may start narrow, under 3 millimeters wide, then gradually widen and darken. The widening usually begins at the base of the nail first. Over time, the nail may split, crack, or deform. If you notice a single dark band under one nail that’s getting wider or spreading into the surrounding cuticle, that’s a specific red flag.
Basal cell carcinoma on darker skin often appears as a glossy brown or black bump with a rolled border. Squamous cell carcinoma can look like a firm bump, scaly patch, or flat sore that’s the same color as your skin, or pink, red, black, or brown. In people with Black and brown skin, squamous cell cancers are more likely to develop in areas that don’t see much sun, including the genitals.
How to Do a Full-Body Skin Check
A thorough self-exam takes about 10 to 15 minutes. The best time is right after a bath or shower, when your skin is clean and you’re already undressed. You’ll need a well-lit room, a full-length mirror, and a hand mirror.
Start by facing the full-length mirror and scanning your entire front, then turn around and check your back. Lift your arms and examine each side, including the often-missed backs of your upper arms. Use the hand mirror to check the back of your neck, your scalp (a comb helps part the hair), your buttocks, and your genital area. Sit down and look at each leg, then the soles of your feet and the spaces between your toes. Check your fingernails and toenails individually for dark streaks. For areas you simply can’t see well, like the middle of your back or the back of your scalp, ask someone you trust to help.
The point of regular self-exams is to build a mental map of your skin so that changes stand out. A mole that’s been the same size and color for years is probably fine. A new spot, or an old spot that’s started to grow, change color, bleed, or itch, is worth showing to a dermatologist. Taking photos of spots you’re unsure about gives you a reference point to compare against next time.
Merkel Cell Carcinoma: Rare but Fast
Merkel cell carcinoma is uncommon, but it grows rapidly and can become dangerous quickly. It usually appears as a painless bump on sun-exposed skin, most often the head or neck in white people and the legs in Black people. The bump is firm, can be pink, purple, red-brown, or skin-colored, and its two sides often don’t match. The key distinguishing feature is speed: if a new bump appears and noticeably grows within weeks, that urgency alone should prompt a visit to a dermatologist.
What Screening Looks Like
There is currently no standard recommendation in the United States for routine skin cancer screening of the general population. The U.S. Preventive Services Task Force has said the evidence is insufficient to recommend for or against clinical visual skin exams in people without symptoms or risk factors. That said, this doesn’t apply to people who have a personal or family history of skin cancer, or anyone who has already noticed a suspicious change. For those individuals, regular professional skin exams are appropriate. For everyone else, monthly self-exams remain the most practical first line of defense, because you know your own skin better than anyone.