What to look for on your skin
Skin cancer usually shows up as a change on your skin — a new spot, a spot that has grown, or a spot that looks different than it did before. The change might be a bump, a patch, a sore that won't heal, or a mark that bleeds or itches. Not every change is cancer, but any change that lasts more than a few weeks or looks unusual enough to worry you is worth showing to a doctor.
The most common sign is a spot that doesn't match the other moles or marks on your body. It might be darker, larger, or have an irregular edge. Some skin cancers are flat; others are raised. Some are skin-colored; others are brown, black, red, or even flesh-toned with a pearly sheen. The variety is wide enough that the only reliable rule is: if it looks wrong to you, it probably should be checked.
Key Takeaways
- Any new spot on your skin, or any existing spot that changes in size, shape, or color over weeks or months, warrants a visit to a doctor or dermatologist.
- The ABCDE rule — Asymmetry, Border irregularity, Color variation, Diameter larger than a pencil eraser, and Evolving (changing) — helps you recognize moles that may be melanoma, the most serious form of skin cancer.
- Spots that itch, bleed, ooze, or refuse to heal are red flags, even if they don't fit the ABCDE pattern perfectly.
- A dermatologist can examine a suspicious spot in minutes and decide whether a biopsy is needed; a biopsy is the only way to confirm whether a spot is cancer.
- Finding skin cancer early, when it is still thin and confined to the surface, makes treatment far more effective and less invasive.
The ABCDE rule for melanoma
Melanoma is the most dangerous form of skin cancer, and doctors use a five-part checklist to spot it. If a mole or spot shows any of these traits, it deserves a closer look:
- Asymmetry: One half of the spot does not match the other half. If you drew a line down the middle, the two sides would look different.
- Border: The edge is jagged, scalloped, or blurry instead of clean and even.
- Color: The spot contains more than one color — brown and black together, or brown and red, or tan and black — rather than a single uniform shade.
- Diameter: The spot is wider than a pencil eraser (about 6 millimeters or one-quarter inch).
- Evolving: The spot has changed in size, shape, or color over weeks or months.
A mole that meets one or two of these criteria is not automatically cancer, but it is worth showing to a dermatologist. A mole that meets three or more should be examined soon. The ABCDE rule is a screening tool, not a diagnosis — only a biopsy can confirm whether a spot is melanoma.
Other warning signs beyond ABCDE
Not all skin cancers are melanoma, and not all dangerous spots fit the ABCDE pattern. Basal cell carcinoma and squamous cell carcinoma — the two most common forms — often look different. They may appear as a waxy bump, a scaly patch, a sore with a raised border, or a spot that bleeds or oozes without an obvious injury.
Pay attention to any spot that itches, hurts, bleeds, or refuses to heal. A sore that scabs over and then opens again, week after week, is a sign to see a doctor. So is a spot that grows visibly over a few months, or a patch of skin that becomes thickened, discolored, or rough. Redness, swelling, or warmth around a mole can also be a warning sign, though these can also be caused by irritation or infection.
Spots on parts of your body that get less sun — your palms, soles, between your toes, or under a fingernail — are less common but still possible. Any unusual mark in these places deserves attention because it is less likely to be a benign sun spot.
When to see a doctor or dermatologist
You do not need to wait for a spot to meet all five ABCDE criteria before you make an appointment. If a spot is new, growing, changing color, or simply looks wrong to you, call your primary care doctor or a dermatologist. Many dermatologists can see you within a few weeks, and some practices keep same-week slots open for suspicious spots.
Your primary care doctor can examine a spot and refer you to a dermatologist if needed. A dermatologist is a doctor who specializes in skin and can often tell at a glance whether a spot needs a biopsy. The exam takes minutes and is painless. If the doctor thinks the spot might be cancer, they will perform a biopsy — removing a small sample of skin to send to a lab for testing. That is the only way to know for certain whether a spot is cancer.
Do not delay because you are worried it might be nothing. Most skin changes are not cancer. But the ones that are cancer are far easier to treat when caught early — before they have grown deep into the skin or spread to other parts of your body.
Risk factors that increase your chances
Knowing your risk does not tell you whether a specific spot is cancer, but it can help you decide how carefully to watch your skin. People with fair skin, light hair, and light eyes have higher risk than people with darker skin, though skin cancer occurs in all skin types. People who have had severe sunburns, especially in childhood, have higher risk. So do people who spend a lot of time outdoors without sun protection, or who use tanning beds.
If you have many moles — more than 50 — your risk is higher than average. If a close relative (parent, sibling, or child) has had melanoma, your risk is also higher. People with a history of skin cancer have higher risk of developing it again. None of these factors means you will definitely get skin cancer, but they mean you should check your skin regularly and see a doctor sooner rather than later if you notice a change.
How to check your own skin regularly
Once a month, spend a few minutes looking at your entire body in a mirror, including spots you cannot see easily — your back, the back of your neck, and the soles of your feet. A hand mirror or a photo taken with your phone can help you see hard-to-reach places. Look for any new spots, or any existing moles or marks that have grown, changed color, or changed shape since the last time you checked.
It helps to take photos of any moles you are watching, so you can compare them month to month. Many people find it useful to sketch a rough map of their moles — marking which ones are on their chest, back, arms, and legs — so they can notice if a new one appears. You are not looking for perfection; you are looking for change. A mole that has stayed the same size and color for years is almost certainly fine. A mole that has changed in the last few months is worth showing to a doctor.
Frequently Asked Questions
Can I tell if a spot is cancer just by looking at it?
No. The ABCDE rule and other warning signs help you recognize spots that need to be checked, but only a biopsy can confirm whether a spot is cancer. Many spots that look suspicious turn out to be benign, and some cancers can look innocent. That is why a doctor's examination matters.
Do all skin cancers start as moles?
No. Skin cancer can develop in a mole you have had for years, but it can also appear as a completely new spot on skin that was previously clear. Some skin cancers grow on skin that has been sun-damaged and looks rough or discolored. Watch for any change, not just changes in existing moles.
What if I have a spot that itches but looks normal?
Itching alone is not a sure sign of cancer — many benign spots itch — but itching combined with other changes (growth, color change, bleeding) is worth reporting to a doctor. If a spot itches persistently and does not improve, show it to your doctor even if it looks normal to you.
How fast does skin cancer grow?
Growth speed varies widely. Some skin cancers grow slowly over months; others grow faster. The important thing is not speed but change — any spot that is visibly different than it was a few months ago deserves attention, whether it grew quickly or slowly.
Should I be worried about every new mole?
New moles are common, especially in younger people and in people who spend time in the sun. Most new moles are benign. Watch new moles the same way you watch old ones: if they stay the same, they are probably fine. If they change, have them checked.