Most moles are harmless, but certain visual and physical changes can signal skin cancer. The key is knowing what to look for and checking regularly. When melanoma is caught early, while still localized to the skin, the five-year survival rate is above 99%. When it’s caught after spreading to distant organs, that number drops to 35%. The difference between those two outcomes often comes down to recognizing warning signs early.
What a Normal Mole Looks Like
Before you can spot something suspicious, it helps to know what’s typical. A normal mole is usually smaller than 5 millimeters wide (roughly the width of a pencil eraser). It’s round or oval with a smooth, distinct edge that clearly separates it from the surrounding skin. The color is even throughout, usually pink, tan, or brown. People with darker skin or hair tend to have darker moles. A normal mole may start flat and eventually become a raised, smooth bump over time, but it doesn’t change rapidly or look dramatically different from your other moles.
The ABCDE Rule for Spotting Melanoma
Dermatologists use a five-letter checklist to evaluate whether a mole looks suspicious. Not every melanoma will show all five features, but even one is worth getting checked.
- 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 and well-defined. The pigment may seem to spread into the surrounding skin.
- Color: Instead of a single even shade, you see a mix of brown, tan, and black, sometimes with patches of white, gray, red, pink, or blue.
- Diameter: The mole is larger than 6 millimeters (about 1/4 inch). Melanomas can be smaller than this, but most are at least this size.
- Evolving: The mole has visibly changed in size, shape, or color over the past few weeks or months.
That last criterion, evolution, is arguably the most important. Any mole that is actively changing deserves attention, even if it doesn’t meet the other criteria. Some aggressive melanomas, called nodular melanomas, can grow at a rate of 0.5 millimeters per month in depth. In one documented case, significant changes were visible within just 10 days. These fast-growing types account for about two-thirds of the thickest, most dangerous tumors, so a rapidly changing spot should never be put off.
The “Ugly Duckling” Approach
The ABCDE rule evaluates a single mole in isolation. The ugly duckling method takes the opposite approach: you compare a mole against all your other moles. Most of your moles will share a general family resemblance in color, size, and shape. If one mole stands out as obviously different from the rest, that’s your ugly duckling, and it warrants a closer look. Dermatologists use this same intrapatient comparison technique in clinical practice, and research has found it significantly improves melanoma detection rates.
Beyond Appearance: Physical Warning Signs
Some warning signs aren’t visual at all. A mole that starts itching when it never did before, becomes tender or painful, bleeds without being scratched or bumped, or develops inflammation around it can indicate a problem. These sensory changes matter just as much as changes in shape or color. If a mole is doing something it wasn’t doing a few months ago, treat that as useful information regardless of how it looks.
Signs of Non-Melanoma Skin Cancer
Melanoma isn’t the only type of skin cancer, and the other types don’t always look like moles. Basal cell carcinoma, the most common form, often appears as a small, shiny, pearly bump that’s pink or flesh-colored, sometimes with tiny visible blood vessels. It can also show up as a flat, pale, scar-like patch or a reddish, itchy area. Squamous cell carcinoma tends to look like a rough, scaly red patch that may crust or bleed, a raised lump, or a wart-like growth.
Both types share one hallmark: a sore that won’t heal. If you have an open sore that oozes or crusts, heals partially, then comes back, that pattern is a classic warning sign. Both basal and squamous cell cancers can also appear as subtle flat areas that look only slightly different from normal skin, making them easy to overlook.
Skin Cancer on Darker Skin
Skin cancer is less common in people with darker skin tones, but it’s often diagnosed later and at a more advanced stage. One reason is that melanoma in darker-skinned individuals frequently appears in places people don’t think to check: the palms of the hands, soles of the feet, under fingernails or toenails, and in the nail bed. This subtype, called acral lentiginous melanoma, has nothing to do with sun exposure and can easily be missed. When performing a self-exam, check these areas carefully regardless of your skin tone. A dark streak under a nail, a discolored patch on the sole of your foot, or an irregularly shaped spot on your palm all deserve professional evaluation.
How to Do a Self-Exam
Regular self-checks can catch changes early, and they only take a few minutes. Stand in front of a full-length mirror and look at your body from the front and back, then raise your arms and check both sides. Bend your elbows to examine the backs of your forearms, your underarms, your fingernails, and your palms. Sit down and check the backs of your legs, the tops and soles of your feet, between your toes, and your toenails. Use a hand mirror to examine your scalp (part your hair to get a good look), the back of your neck, your back, and your buttocks.
The goal isn’t to diagnose yourself. It’s to notice change. Taking photos of moles you want to track can make it much easier to spot subtle shifts in size, shape, or color over time. If you notice anything new, growing, or different, that’s your signal to get a professional evaluation.
What Happens at the Dermatologist
If a mole looks suspicious, your dermatologist will likely recommend a biopsy, which means removing all or part of the spot so it can be examined under a microscope. There are a few types. A shave biopsy takes a thin slice from the top layers of skin. A punch biopsy goes deeper, removing a small cylinder that includes the upper fat layer. An excisional biopsy removes the entire mole along with a margin of normal skin around it. An incisional biopsy takes only a portion of the growth. The type used depends on the size, location, and how suspicious the spot appears. Most biopsies are done in the office with local numbing and take only minutes. Results typically come back within one to two weeks.
If the biopsy confirms cancer, the next steps depend on the type, thickness, and whether it has spread. But the critical point is this: the earlier it’s caught, the simpler and more effective the treatment. Localized melanoma has that greater-than-99% five-year survival rate. The stakes of early detection are genuinely that high.