Skin cancer often announces itself through visible changes you can spot yourself: a mole that looks different from the rest, a sore that won’t heal, or a new growth that keeps changing. The key is knowing exactly what to look for and where to look, because catching it early makes a dramatic difference. When melanoma is found before it spreads, the five-year survival rate is effectively 100%. Once it reaches distant parts of the body, that drops to 34%.
The ABCDE Rule for Melanoma
Melanoma is the most dangerous form of skin cancer, but it’s also one of the most recognizable if you know the pattern. Dermatologists use a five-feature checklist called the ABCDE rule to evaluate suspicious moles and spots:
- Asymmetry: One half of the mole doesn’t match the other. Normal moles are roughly symmetrical.
- Border: The edges are ragged, notched, or blurred rather than smooth. The pigment may seem to bleed into the surrounding skin.
- Color: Instead of one uniform shade, you see a mix of brown, black, tan, white, gray, red, pink, or blue within the same spot.
- Diameter: The spot is larger than 6 millimeters across (roughly the size of a pencil eraser). Melanomas can be smaller, but most exceed this threshold.
- Evolving: The mole has changed in size, shape, or color over the past few weeks or months. Any noticeable change is worth attention.
You don’t need all five features to be concerned. Even one or two, especially evolution, is enough reason to have a dermatologist take a closer look.
The “Ugly Duckling” Sign
Beyond the ABCDE checklist, there’s a simpler and surprisingly effective screening trick: look for the mole that doesn’t match the others. Most people’s moles share a general “family resemblance” in color, size, and shape. If one spot stands out as clearly different from the rest, that outlier is the most suspect for malignancy. Researchers in the Journal of Clinical and Aesthetic Dermatology found that the ugly duckling approach and the ABCDE rule complement each other, catching cases the other might miss. Using both together gives you the best chance of spotting something early.
What Non-Melanoma Skin Cancer Looks Like
Melanoma gets the most attention, but basal cell carcinoma and squamous cell carcinoma are far more common. They look quite different from suspicious moles, and many people don’t recognize them as cancer at all.
Squamous cell carcinoma often appears as a firm bump or nodule on the skin. It can be pink, red, brown, or black depending on your skin tone. It may also show up as a flat sore with a scaly crust, a rough patch on the lip that becomes an open sore, or a new raised area on an old scar. The hallmark clue: a sore or scab that doesn’t heal within about two months.
Basal cell carcinoma typically appears as a pearly or waxy bump, a flat flesh-colored or brown scar-like patch, or a sore that heals and then reopens. It tends to develop on sun-exposed areas like the face, ears, and neck. Like squamous cell, it rarely causes pain in the early stages, which is why people often dismiss it.
Spots That Look Like Cancer but Aren’t
Not every alarming-looking spot is dangerous. Seborrheic keratoses are one of the most common benign growths that people mistake for skin cancer. They can range from black to white, often appear patchy, and look waxy or like an unusual scab. They’re typically flat, painless, and can pop up anywhere on the body. The tricky part is that in some people, a melanoma can look like a seborrheic keratosis. If you’re not sure, a dermatologist can usually tell the difference with a physical exam, and when they can’t, a biopsy settles it quickly.
Pre-Cancerous Patches to Watch
Actinic keratoses are rough, dry, scaly patches of skin, usually less than an inch across, that develop from years of sun exposure. They may be pink, red, or brown, and they sometimes itch, burn, or bleed. On their own, they’re not cancer. But left untreated, about 5% to 10% of actinic keratoses progress to squamous cell carcinoma. If you notice rough patches that won’t go away on sun-exposed skin (scalp, face, forearms, backs of hands), getting them evaluated and treated early prevents that progression entirely.
Skin Cancer on Darker Skin
There’s a persistent misconception that people with dark skin don’t get skin cancer. They do, and the cancers are often diagnosed later because neither the patient nor their doctor was looking for them. The most common melanoma in people with dark skin is acral lentiginous melanoma, which appears in places most people never think to check: the palms of the hands, the soles of the feet, under fingernails and toenails, and between fingers and toes. It can look like a dark patch on your palm or sole, or a dark band running under a nail. These areas have little to do with sun exposure, which is part of why they’re overlooked. If you have darker skin, pay special attention to these areas during self-exams.
How to Do a Monthly Self-Exam
The Skin Cancer Foundation recommends checking your entire body once a month. You’ll need a bright light, a full-length mirror, a hand mirror, and a blow-dryer for your scalp. The whole process takes about 10 minutes once you’re familiar with it.
Start with your face, including your nose, lips, mouth, and ears (front and back). Use the blow-dryer to part sections of your scalp so you can see the skin underneath. Check your hands carefully: palms, backs, between the fingers, and under each fingernail. Move to your neck, chest, and torso, lifting the breasts to check underneath. Examine the front of your arms, then use the full-length mirror and hand mirror together to scan your upper back, shoulders, lower back, and buttocks. Finally, check the front and back of both legs, your feet (tops, soles, and between toes), and your toenails.
The point of doing this monthly isn’t to diagnose yourself. It’s to build a mental map of your skin so you notice when something changes. A spot that was flat and is now raised, a mole that’s gotten darker, a sore that appeared and won’t close. These are the changes that matter.
What Happens if Something Looks Suspicious
If you or a dermatologist finds a spot that needs further evaluation, the next step is a skin biopsy. This is a quick in-office procedure where a small sample of skin is removed and examined under a microscope. There are a few types depending on the situation. A shave biopsy takes a thin section from the top layers of skin. A punch biopsy goes deeper, removing a small cylinder that includes the top skin layers and the fat layer beneath. An excisional biopsy removes the entire growth along with a border of healthy skin around it.
The biopsy is the only way to confirm whether a spot is cancerous. Visual assessment, even by experienced dermatologists, has limits. Many spots that look suspicious turn out to be benign, and occasionally a spot that looks harmless turns out not to be. The biopsy removes the guesswork, and results typically come back within a week or two.