Skin cancer doesn’t always look dramatic or obvious. It can show up as a small shiny bump, a scaly patch that won’t heal, a changing mole, or even a dark streak under a fingernail. The key to catching it early is knowing what to look for on your specific skin and paying attention when something changes or doesn’t look like everything else around it.
The ABCDE Rule for Suspicious Moles
The most widely used guide for spotting melanoma, the most dangerous form of skin cancer, is the ABCDE rule. Each letter flags a specific warning sign in a mole or dark spot:
- Asymmetry: One half of the mole doesn’t match the other half in shape.
- Border irregularity: The edges are ragged, notched, or blurred rather than smooth and round. Pigment may spread into surrounding skin.
- Color variation: Instead of one uniform shade, you see a mix of brown, tan, black, or even patches of white, gray, red, pink, or blue.
- Diameter: Most melanomas are larger than about 6 millimeters (roughly the size of a pencil eraser), though they can start smaller.
- Evolving: The mole has changed in size, shape, color, or texture over the past few weeks or months.
You don’t need all five features to be concerned. Even one, especially a mole that’s clearly evolving, is enough reason to have it looked at.
The “Ugly Duckling” Sign
If you have lots of moles or freckles, the ABCDE rule can feel overwhelming. A simpler filter is the ugly duckling sign: look for the one spot that doesn’t match the rest. Most of your moles probably share a general look, whether that’s small and flat, round and brown, or slightly raised. The spot that stands out, maybe it’s scabbed over, more raised, darker, or has grown while the others haven’t, is the one worth watching. Just like in the childhood story, the one that doesn’t fit in deserves closer attention.
What Basal and Squamous Cell Cancers Look Like
Melanoma gets the most attention, but basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) are far more common. They look quite different from a suspicious mole, and people often dismiss them as minor skin irritations.
Basal cell carcinoma tends to appear on sun-exposed areas like the face, ears, and neck. On lighter skin, it often shows up as a small pink or red bump with a pearly, translucent quality. Sometimes it looks like a flat, pale, scar-like patch, or a pink growth with raised edges and visible blood vessels spreading outward from the center. It can also appear as a reddish patch that itches.
Squamous cell carcinoma often looks rougher. Think scaly red patches that may crust or bleed, raised lumps with a dip in the center, or growths that resemble warts. Both BCC and SCC can also appear as open sores that ooze or crust over, seem to heal, then come back. That cycle of healing and reopening is a hallmark worth paying attention to. And both types can sometimes show up as a flat area with only subtle changes from the surrounding skin, making them easy to overlook.
Precancerous Patches That Mimic Age Spots
Actinic keratoses are rough, scaly patches caused by years of sun exposure. They’re not cancer yet, but they can develop into squamous cell carcinoma if left untreated. The tricky part is that they often look like ordinary age spots or minor skin irritation, especially on darker skin tones where they tend to appear as flat, scaly areas that closely resemble sun spots.
You can often feel an actinic keratosis before you can see it. Run your fingers over sun-exposed skin like the face, scalp, backs of the hands, and forearms. A sandpaper-like rough spot that doesn’t go away is worth noting. These patches can itch, sting, feel tender when touched, or even catch on clothing. Some look like pimples or a persistent rash. Multiple rough bumps appearing together in a sun-exposed area is a common pattern.
Skin Cancer on Darker Skin Tones
Skin cancer is less common in people with darker skin, but it’s often caught later because both patients and doctors may not be looking for it in the right places. The most common form of melanoma in people of color is acral lentiginous melanoma, which develops on the palms of the hands, soles of the feet, and under the nails. These are areas that get little sun exposure, so the usual sun-damage mindset doesn’t apply.
On the sole of the foot or palm of the hand, it typically starts as a black or brown discoloration that resembles a bruise or stain. Over time, it grows. Under a fingernail or toenail, it usually appears as a dark vertical streak running the length of the nail, sometimes mistaken for a fungal infection or blood under the nail. As it progresses, it can cause the nail to crack or break. If you notice a dark stripe under a nail that isn’t linked to an injury, or a “bruise” on your palm or sole that doesn’t fade after a couple of weeks, get it checked.
How to Do a Full Self-Exam
A thorough skin check takes about 10 minutes and requires a full-length mirror, a hand mirror, and good lighting. The American Academy of Dermatology recommends a head-to-toe sequence:
Start by standing in front of a full-length mirror and looking at your body from the front, then turn to see each side with your arms raised. Bend your elbows and carefully check your forearms, underarms, fingernails, and palms. Next, examine the backs of your legs, the spaces between your toes, your toenails, and the soles of your feet. Use a hand mirror to look at the back of your neck and scalp, parting your hair as you go. Finally, use the hand mirror to check your back and buttocks.
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 existing changes. Doing this once a month gives you a reliable baseline. Taking photos of moles you want to track can make it easier to spot changes over time.
What Happens if You Find Something Suspicious
If you spot something that matches any of the patterns above, the next step is a visit to a dermatologist. There’s no universal recommendation for routine skin cancer screening in people with no symptoms or history of skin cancer, which means catching something early often comes down to your own awareness and action.
When a dermatologist evaluates a suspicious spot, they’ll first examine it visually, often using a dermatoscope (a magnifying tool with a light). If the spot looks concerning, they’ll do a biopsy, which is a quick in-office procedure. After cleaning the area and injecting a local anesthetic so you won’t feel anything, they remove a small sample of skin. For a shave biopsy, they take a thin surface layer with no stitches needed. A punch biopsy removes a small circular core of deeper tissue, typically closed with a stitch or two. An excisional biopsy removes a larger piece and also requires stitches.
Afterward, you’ll keep the area clean and bandaged while it heals. The sample goes to a lab where it’s examined under a microscope. Results usually come back within one to two weeks. If the biopsy confirms skin cancer, your dermatologist will discuss removal options based on the type, size, and location. Most non-melanoma skin cancers caught early are highly treatable with outpatient procedures.
Red Flags That Deserve Prompt Attention
Some changes are more urgent than others. A mole that’s rapidly growing, bleeding without being bumped, or changing color over just a few weeks warrants a sooner appointment rather than a “wait and see” approach. The same goes for any new, firm, painless bump on sun-exposed skin that’s growing quickly, particularly if you’re over 50 or have a weakened immune system. A sore anywhere on your body that hasn’t healed in three to four weeks also deserves evaluation, even if it doesn’t look like what you’d picture as cancer. Skin cancer is often more subtle than people expect, and the absence of pain doesn’t mean the absence of a problem.