Melanoma is the most dangerous form of skin cancer, but when caught early and still confined to the skin, the five-year survival rate is effectively 100%. Once it spreads to distant parts of the body, that number drops to 34%. The difference between those two outcomes often comes down to spotting it early, and you can learn to do that yourself.
The ABCDE Rule
Most melanomas on the skin’s surface share a set of visual warning signs captured by five letters: A, B, C, D, and E.
- Asymmetry. One half of the mole doesn’t match the other. A normal mole is roughly symmetrical; melanoma tends to grow unevenly.
- Border irregularity. The edges are ragged, notched, or blurred rather than smooth. Pigment may bleed outward into the surrounding skin.
- Color variation. Instead of a single uniform shade, the spot contains a mix of brown, tan, and black, sometimes with patches of white, gray, red, pink, or blue.
- Diameter. Most melanomas are larger than about 6 millimeters across, roughly the size of a pencil eraser. But they can start smaller, so size alone isn’t enough to rule one out.
- Evolving. The mole has changed in size, shape, color, or texture over weeks or months. Any mole that looks different from how it looked before deserves attention.
You don’t need all five features to be suspicious. A single one, especially evolution, is enough reason to have a spot checked.
The Ugly Duckling Sign
The ABCDE rule evaluates one mole at a time, but there’s a complementary approach that’s surprisingly effective: look for the outlier. Most of your moles tend to resemble each other in size, shape, and color. A mole that looks obviously different from all the others on your body is called an “ugly duckling,” and it may be more concerning than a mole that simply has an irregular border.
In clinical studies, comparing moles to one another on the same person rather than analyzing each mole in isolation improved specificity to around 95-96%. It also reduced the number of moles flagged for biopsy by nearly sevenfold. In practical terms, this means stepping back and scanning your skin for the one spot that just doesn’t fit in with the rest.
Nodular Melanoma Looks Different
Not all melanomas spread outward across the skin’s surface. Nodular melanoma grows downward into the skin from the start, which makes it more aggressive and harder to catch with the ABCDE rule alone. It often appears as a firm, raised bump that may be uniformly dark or even skin-colored, so it can lack the irregular borders and color variation you’d normally look for.
For this type, the EFG rule is more useful:
- Elevated. The lesion is raised above the skin surface.
- Firm. It feels solid to the touch, not soft or squishy.
- Growing. It’s getting larger over weeks or months.
Any new bump that feels firm and keeps growing should be evaluated, even if it doesn’t look like a typical mole.
Melanoma in Hidden Locations
Melanoma doesn’t only appear on sun-exposed skin. It can develop in places most people never think to check.
Palms, Soles, and Under the Nails
Acral lentiginous melanoma shows up on the palms of the hands, soles of the feet, or under the nails. On the palms and soles, it typically starts as a brown or black discoloration that looks like a bruise or stain but continues to grow. Under the nails, it appears as a dark vertical streak running the length of the nail bed, sometimes mistaken for dried blood or a fungal infection. As it progresses, the nail may crack or break. This is the most common type of melanoma in people with darker skin tones.
Mucosal Melanoma
Melanoma can also arise on mucous membranes, the moist tissue lining the mouth, nose, throat, and genital or anal areas. These are rare but easy to miss because the symptoms mimic other common problems. A sore in the mouth that won’t heal, repeated nosebleeds from one nostril, rectal bleeding, or vaginal bleeding between periods or after menopause can all be signs. Because these locations aren’t visible during a typical skin check, they’re often diagnosed at a later stage.
How to Do a Self-Exam
A thorough skin check takes about 10 to 15 minutes and should cover your entire body. You’ll need a full-length mirror, a hand mirror, and good lighting.
Start with your face, ears, and neck. Move to your chest and torso, lifting any skin folds. Check both arms, including the undersides, and look between your fingers and at your palms. Sit down and examine the fronts and backs of your legs, the tops and soles of your feet, and between your toes. Use the hand mirror to check the back of your neck, your scalp (part your hair section by section), your back, and your buttocks. Don’t skip your genital area.
The goal is to build a mental map of your moles so you notice when something changes. Some people take photos of concerning spots to compare over time. Doing this regularly, whether monthly or every few months, makes changes far easier to catch.
Your Mole Count Matters
The number of moles on your body is one of the strongest predictors of melanoma risk. People with more than 100 common moles have roughly seven times the risk of someone with 15 or fewer. Having five or more atypical moles (moles that are larger, irregularly shaped, or unevenly colored but not cancerous) raises risk about sixfold.
A quick way to estimate your total mole count without undressing completely: count the moles on one arm. If you have 11 or more on a single arm, you likely have more than 100 on your entire body, which places you in a higher-risk category worth discussing with a dermatologist.
What Happens If a Spot Looks Suspicious
A dermatologist will first examine the spot using dermoscopy, a handheld magnifying device with polarized light that reveals structures beneath the skin’s surface invisible to the naked eye. A large Cochrane review found that dermoscopy is roughly four to five times more accurate than visual inspection alone. At the same level of specificity (80%), dermoscopy detects about 92% of melanomas compared to 76% with the naked eye.
If the spot still looks concerning after dermoscopy, the next step is a biopsy. The preferred method for suspected melanoma is an excisional biopsy, where the entire lesion is removed along with a small margin of surrounding skin and a layer of tissue beneath it. This approach is important because accurately measuring how deep the melanoma extends into the skin determines the stage and guides every treatment decision that follows. A partial or shallow biopsy risks cutting through the base of the tumor, which can compromise that measurement.
The biopsy itself is done under local anesthesia in a clinic and typically takes less than 30 minutes. Results usually come back within one to two weeks.
Why Early Detection Changes Everything
Melanoma survival is almost entirely a function of how early it’s found. When the cancer is still localized to the skin, the five-year relative survival rate is 100%. Once it reaches nearby lymph nodes, survival drops to 76%. If it has spread to distant organs like the lungs, liver, or brain, the five-year survival rate falls to 34%. These numbers, based on SEER data from 2016 to 2022, make a clear case: the same cancer caught at different times produces drastically different outcomes. A few minutes of regular self-examination is one of the simplest ways to stay on the right side of those statistics.