What skin cancer looks like and what to watch for
Skin cancer usually shows up as a change on your skin—a new spot, a mole that looks different than it did before, or a patch that doesn't heal. The most common types are basal cell carcinoma, squamous cell carcinoma, and melanoma. Not every change means cancer, but knowing what to look for helps you catch something early, when treatment works best.
The ABCDE rule is the standard way to spot melanoma, the most serious type. Look for: Asymmetry (one half doesn't match the other), Border irregularity (edges are jagged or blurry), Color variation (multiple colors in one spot), Diameter larger than a pencil eraser, and Evolving (changing in size, shape, or color). If a mole or spot has any of these traits, that's a reason to see a dermatologist.
Basal cell and squamous cell carcinomas often look different. They may appear as a shiny bump, a scaly patch, a sore that doesn't heal after a few weeks, or a waxy or pearly nodule. They grow slowly and are less likely to spread than melanoma, but they still need treatment.
Key Takeaways
- Use the ABCDE rule to check moles: asymmetry, irregular border, multiple colors, diameter larger than a pencil eraser, and evolving appearance are all warning signs.
- A sore or patch that doesn't heal in three to four weeks, especially on the face, ears, or hands, warrants a doctor's visit.
- Basal cell and squamous cell carcinomas often look like shiny bumps, scaly patches, or waxy nodules rather than irregular moles.
- Perform a full-body skin check once a month, including your scalp, between your toes, and your back—areas you don't see every day.
- A dermatologist can diagnose skin cancer with a biopsy; you cannot know for certain whether a spot is cancer without one.
How to do a monthly skin check at home
Set a routine—the first of each month works well—and check your entire body in front of a mirror. Use a handheld mirror to see your back, and ask a partner or family member to check your scalp and the back of your neck if possible. Pay special attention to areas that get sun exposure: your face, ears, chest, shoulders, arms, and legs.
Look for anything new or anything that has changed. Take a photo of any spot you're unsure about so you can compare it over time. If you notice a mole or patch that looks different from your others, or if it matches any part of the ABCDE rule, write down the date and location. Bring this information to your doctor.
Don't panic over every spot. Most skin changes are not cancer. But tracking changes gives you and your doctor real information to work with, rather than guessing whether something matters.
When to see a dermatologist
See a dermatologist if you notice a new mole or spot, if an existing mole has changed in size, shape, or color, or if you have a sore or patch that hasn't healed in three to four weeks. You should also go if a spot itches, bleeds, or feels tender, or if anything on your skin simply looks wrong to you.
You don't need to wait for a spot to meet all five ABCDE criteria. Even one or two signs are worth having checked. Dermatologists are trained to spot the difference between a harmless mole and something that needs treatment, and they can do a biopsy—a small tissue sample—to know for certain.
If you have a family history of skin cancer, many dermatologists recommend an annual full-body check even if you don't see anything concerning. Ask your primary care doctor for a referral to a dermatologist in your area.
Risk factors that increase your chances
Fair skin, a history of sunburns, and time spent in the sun all raise your risk. So do a family history of skin cancer and a large number of moles. If you have any of these risk factors, check your skin more often—every two weeks rather than monthly—and see a dermatologist yearly.
People with darker skin can develop skin cancer too, though it's less common. When it does occur, it's often found later because people assume they're not at risk. Skin cancer in people with darker skin often appears on the palms, soles, or under the nails. Check these areas carefully during your monthly exam.
Age matters as well. Skin cancer becomes more common as you get older, but it can happen at any age. Melanoma is one of the most common cancers in people under 30, so don't assume you're too young to worry.
What happens at a dermatology appointment
The dermatologist will look at the spot with their eyes and sometimes with a magnifying tool called a dermatoscope. They'll ask how long it's been there, whether it's changed, and whether it itches or bleeds. If they think it might be cancer, they'll do a biopsy—they remove a small piece of skin (usually with local numbing) and send it to a lab.
A biopsy is the only way to know for certain whether a spot is cancer. The procedure takes a few minutes, and you get results in a week or two. If the biopsy shows cancer, your dermatologist will talk with you about treatment options, which depend on the type and stage of cancer.
If the biopsy is normal, you can stop worrying about that particular spot. Your dermatologist may still recommend sun protection and regular checks, especially if you have other risk factors.
Sun protection to lower your risk
Limiting sun exposure is the most effective way to prevent skin cancer. Wear sunscreen with SPF 30 or higher every day, even on cloudy days and in winter. Reapply every two hours if you're outside, and after swimming or sweating. Sunscreen alone isn't enough—wear protective clothing, a hat, and sunglasses when you're in the sun for long periods.
Avoid tanning beds. They emit ultraviolet radiation that increases skin cancer risk, especially in people under 35. The risk is real and doesn't depend on how often you use them.
If you've already had skin cancer, sun protection becomes even more important. People who've had one skin cancer are at higher risk for another. Your dermatologist can give you specific recommendations based on your history.
The difference between what you see and what a biopsy shows
Your eyes and a dermatologist's eyes are good at spotting spots that need checking, but they can't diagnose cancer. A mole can look suspicious and turn out to be harmless. A spot that looks minor can be cancer. This is why a biopsy matters—it's the actual answer, not a guess.
Conversely, some people worry that checking a spot or having a biopsy will "spread" cancer. This is not true. A biopsy is a safe procedure and won't make cancer worse or cause it to spread. Getting checked early, when cancer is small, actually improves outcomes.
Frequently Asked Questions
Can I tell if a mole is cancer just by looking at it?
No. A dermatologist can make an educated guess based on experience, but only a biopsy—a tissue sample sent to a lab—can confirm whether something is cancer. Many harmless moles look suspicious, and some cancers look innocent. If you're unsure, see a dermatologist rather than trying to diagnose yourself.
Does sunscreen prevent all skin cancer?
Sunscreen reduces risk significantly, but it's not perfect. It works best when combined with protective clothing, hats, and limiting time in direct sun. Even people who use sunscreen regularly can develop skin cancer, which is why monthly skin checks matter.
What if I find a spot that matches the ABCDE rule?
Call a dermatologist and describe what you see. Most offices can fit you in within a few weeks. If the spot is bleeding, growing quickly, or causing pain, mention that when you call—it may move you up in the schedule. Don't wait months to have it checked.
Is skin cancer always visible on the surface?
Most skin cancers start on the surface where you can see them, which is why regular checks work. However, melanoma can occasionally develop deeper in the skin. This is another reason to see a dermatologist if something feels different, even if it doesn't look obviously wrong.
What should I do if I have lots of moles?
People with many moles have higher skin cancer risk. Take photos of your moles and compare them monthly to spot changes. See a dermatologist yearly, or more often if your doctor recommends it. Your dermatologist may photograph your moles to track them over time.