Skin cancer shows up in surprisingly different ways depending on the type, and no single sign covers all of them. The most reliable approach combines knowing what to look for with regular self-checks so you notice when something changes. Here’s what each type looks like, how to examine yourself, and which warning signs should send you to a dermatologist.
The Three Main Types Look Different
Skin cancer isn’t one disease. The three most common types each have distinct appearances, and recognizing those differences matters because you might dismiss something dangerous simply because it doesn’t match your mental image of what skin cancer “should” look like.
Basal Cell Carcinoma
This is the most common skin cancer, and it rarely looks alarming at first. On lighter skin, it often appears as a firm, raised, round growth that’s shiny and pink or red. On darker skin tones, it tends to be black, brown, or blue. Some basal cell carcinomas have a dip in the center that may scab over and bleed. Others look like a rough, scaly patch, or a spot resembling a freckle or age spot that feels scaly to the touch. One hallmark: a sore that heals and then returns, or simply never heals at all.
Squamous Cell Carcinoma
Squamous cell carcinoma often shows up as a firm bump (called a nodule) that can 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 or scaly patch on the lip that becomes an open sore, or a new raised area developing on an old scar. These growths tend to appear on sun-exposed areas but can also develop inside the mouth or on the genitals.
Melanoma
Melanoma is the least common of the three but the most dangerous. It typically develops in or near an existing mole, or appears as a new dark spot. The standard screening tool is the ABCDE rule, developed by the National Cancer Institute:
- Asymmetry: One half of the mole doesn’t match the other.
- Border: The edges are ragged, notched, or blurred, and pigment may spread into surrounding skin.
- Color: Multiple shades are present, including black, brown, tan, white, gray, red, pink, or blue.
- Diameter: Most melanomas are larger than 6 millimeters (about the size of a pencil eraser), though they can be smaller.
- Evolving: The mole has changed in size, shape, or color over recent weeks or months.
The Ugly Duckling Method
The ABCDE rule works well for evaluating a single mole, but there’s a complementary approach that’s just as useful. Most of your normal moles resemble one another in size, shape, and color. A melanoma often stands out like an “ugly duckling,” looking noticeably different from its neighbors. That difference could mean it’s larger, smaller, lighter, or darker than surrounding moles. A completely isolated lesion with no similar-looking moles nearby also qualifies as an ugly duckling worth watching. If a spot catches your eye specifically because it doesn’t match the rest, that instinct is worth following up on.
Skin Cancer on Darker Skin
Skin cancer in people of color often appears in locations that don’t get much sun exposure, which means it’s frequently missed. Acral lentiginous melanoma, the most common melanoma subtype in people of color, shows up as a black or brown discoloration on the sole of the foot or palm of the hand. A related form develops under fingernails or toenails, appearing as dark vertical streaks running across the nail bed. This type is often mistaken for a bruise or fungal infection, which can delay diagnosis significantly. If you have a dark streak in a nail that wasn’t caused by injury, or a discolored patch on your palms or soles that won’t go away, get it evaluated.
Pre-Cancerous Spots to Watch
Not everything concerning on your skin is cancer yet. Actinic keratoses are rough, scaly patches caused by years of sun exposure. They’re considered precancerous because some can progress to squamous cell carcinoma over time. These patches tend to lie flat on the head and neck but appear as raised bumps on the arms and hands. The base color varies widely: light, dark, tan, pink, red, or skin-colored. They often feel dry, rough, or horny to the touch, and some itch or feel prickly. Treating them early eliminates the risk of progression.
How to Do a Self-Exam
You need a full-length mirror, a hand mirror, and good lighting. The American Academy of Dermatology recommends a specific sequence to make sure you don’t miss anything:
- Stand in front of a full-length mirror and examine your body front and back.
- Raise your arms and check your right and left sides.
- Bend your elbows and look carefully at your forearms, underarms, fingernails, and palms.
- Check the backs of your legs, feet, the spaces between your toes, your toenails, and the soles of your feet.
- Use a hand mirror to examine the back of your neck and scalp, parting your hair for a closer look.
- Finally, use the hand mirror to check your back and buttocks.
Do this once a month. The goal isn’t to diagnose anything yourself. It’s to build a mental map of your skin so you notice when something new appears or something familiar changes. Taking photos of spots you want to track makes it easier to detect subtle shifts over time.
Skip the Skin Cancer Apps
Smartphone apps that claim to analyze photos of your skin for cancer are not reliable. A study overseen by Memorial Sloan Kettering Cancer Center dermatologists found that commercial skin cancer detection apps were only 59% accurate on average. Worse, the algorithms performed terribly on diagnoses they hadn’t been trained on, dropping to about 6% accuracy. The most dangerous problem isn’t false alarms. It’s the opposite: these apps may create a false sense of security by failing to flag actual melanomas. Your eyes and a mirror are more useful than any app currently on the market.
When to See a Dermatologist
There’s no formal recommendation for routine skin cancer screening in people without symptoms or risk factors. The U.S. Preventive Services Task Force says there isn’t enough evidence to assess whether visual screening by a clinician helps the general population. That changes entirely if you have a personal or family history of skin cancer, or if you’ve noticed something concerning.
See a dermatologist if any spot on your skin hurts, bleeds, itches, or isn’t going away. See one if a spot looks dramatically different from other spots on your body. MD Anderson Cancer Center puts it simply: if you wrinkle your brow and think “What on earth is that?” when you see a spot, that’s reason enough. If you’re genuinely worried about a skin change, that worry alone is a valid reason to book an appointment.
Try to get in as soon as possible if you’re concerned. Most skin cancers should be treated within two or three months of diagnosis, so while the timeline isn’t usually a matter of days, you don’t want to sit on it for months either.