Most moles are harmless, but certain visual changes can signal melanoma or other skin cancers. The five-year survival rate for melanoma caught at an early, localized stage is 97.6%, compared to just 16.2% when it has spread to distant parts of the body. That gap makes knowing what to look for genuinely life-saving.
The ABCDE Rule
Dermatologists use a five-feature checklist to evaluate whether a mole looks suspicious. You don’t need all five to be present for concern. Even one is worth getting checked.
- Asymmetry. One half of the mole doesn’t match the other. A normal mole is roughly symmetrical if you imagine folding it in half.
- Border. The edges are ragged, notched, or blurred rather than smooth and well-defined. Pigment may appear to spread into the surrounding skin.
- Color. The mole contains multiple shades, such as brown, tan, and black mixed together. Areas of white, gray, red, pink, or blue are particularly concerning.
- Diameter. Most melanomas are larger than 6 millimeters wide (about the size of a pencil eraser). However, melanomas can be smaller than this, so size alone isn’t enough to rule one out.
- Evolving. The mole has changed in size, shape, color, or texture over the past few weeks or months. Any noticeable change in a previously stable mole deserves attention.
The Ugly Duckling Sign
Your moles tend to look like each other. They share a general pattern of size, shape, and color that’s unique to your skin. The “ugly duckling” sign is simply this: if one mole looks noticeably different from all the others on your body, it’s worth flagging. Dermatologists use this approach alongside the ABCDE rule because it can catch melanomas that don’t fit the standard checklist. A mole that’s an outlier compared to your other moles is suspicious precisely because it doesn’t belong.
Skin Cancers That Don’t Look Like Moles
Not all skin cancers start in an existing mole. Basal cell carcinoma and squamous cell carcinoma often appear as entirely new growths. Squamous cell carcinoma can show up as a firm bump (sometimes the same color as your skin, sometimes pink, red, or brown), a flat sore with a scaly crust, a rough patch on your lip that turns into an open sore, or a new raised area on an old scar.
The key warning sign for these cancers is a sore or scab that won’t heal. If you have a spot that hasn’t healed within about two months, or a scaly patch that keeps coming back, that’s a red flag even if it looks nothing like a typical mole.
Signs on Darker Skin, Palms, and Nails
Melanoma on the palms, soles, and under the nails (called acral melanoma) is frequently misdiagnosed as a fungal infection, wart, or ulcer. This type occurs in all skin tones but accounts for a larger proportion of melanoma cases in people with darker skin. It’s often caught at later stages because people aren’t looking for cancer in these locations.
On the palms or soles, watch for a colored spot that’s enlarging, bleeding, or not healing. Under the nail, the most common sign is a dark streak running lengthwise along the nail plate. Streaks that are black or gray, irregularly colored, wider than two-thirds of the nail, or that cause pigmentation to spread into the skin around the nail are all concerning. These signs are worth getting examined promptly rather than waiting.
Some melanomas have no pigment at all. These “amelanotic” melanomas are the hardest to spot. Look for a spot that is elevated, firm, and growing, even if it has no unusual color.
How to Do a Monthly Skin Check
Checking your skin about once a month gives you the best chance of catching changes early. Do it after a bath or shower in a well-lit room, using a full-length mirror and a hand mirror for hard-to-see areas.
Start with your entire front and back in the full-length mirror. Raise your arms and look at both sides of your body. Bend your elbows to check your forearms, upper arms, palms, and between your fingers. Use the hand mirror to examine the back of your neck, your scalp (parting your hair in sections), behind your ears, and your back. Check the soles of your feet, between your toes, and your nails. Look inside your mouth, including your lips, tongue, and inner cheeks.
The goal isn’t to diagnose anything yourself. It’s to notice change. Taking photos of moles you want to track makes it much easier to spot subtle shifts over time. For people at higher risk (many moles, family history of melanoma, prior skin cancer), dermatologists sometimes offer total body photography, where clinical images of your entire skin surface are taken and stored digitally so any new or changing spots can be identified at future visits.
What Happens if a Mole Looks Suspicious
A dermatologist will first examine the mole visually, often using a handheld magnifying device that lights and magnifies the skin’s surface. If the mole still looks concerning, the next step is a biopsy, which means removing some or all of the mole so it can be examined under a microscope. This is the only way to confirm whether a mole is cancerous.
There are a few types of biopsy depending on the size and depth of the spot. A shave biopsy removes a thin layer from the top and usually doesn’t require stitches. A punch biopsy uses a small circular tool to take a deeper sample and may need a stitch or two. An excisional biopsy removes the entire mole along with a border of healthy skin and typically requires stitches. The procedure is done with local numbing and takes minutes. Results usually come back within one to two weeks.
If the biopsy shows melanoma, the thickness of the tumor determines what happens next. Thin melanomas caught early often need only a wider excision of the surrounding skin to ensure clean margins. Thicker or more advanced melanomas may require additional testing and treatment. This is why catching changes early matters so much: the difference between a simple outpatient procedure and a complex treatment plan often comes down to how quickly the melanoma was found.