Melanoma often first appears as a new or changing mole on the skin, but it can also show up in places you’d never think to check, like under a fingernail, inside your mouth, or in your eye. 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 drops to 34%. Knowing what to look for makes an enormous difference.
The ABCDE Rule for Spotting Melanoma
The most widely used framework for evaluating a suspicious mole is the ABCDE rule, developed by the National Cancer Institute. Each letter flags a specific visual feature of early melanoma:
- Asymmetry. One half of the mole doesn’t match the other. Most normal moles are roughly symmetrical.
- Border irregularity. The edges look ragged, notched, or blurred rather than smooth. Pigment may seem to bleed into the surrounding skin.
- Color variation. Instead of one uniform shade, you see a mix of brown, tan, and black, sometimes with patches of white, gray, red, pink, or blue.
- Diameter. Most melanomas are larger than 6 millimeters across (roughly the size of a pencil eraser), though they can be smaller.
- Evolving. The mole has changed in size, shape, color, or texture over recent weeks or months. Any visible change in a previously stable mole is worth attention.
No single feature is a guaranteed sign of melanoma. A mole can be asymmetrical and completely harmless, or it can look mostly normal but be evolving in a way that matters. The more of these features a spot has, the more reason to get it checked.
The Ugly Duckling Sign
Your moles tend to look like each other. They share a general family resemblance in color, size, and shape. The “ugly duckling” sign is simply this: one mole that looks noticeably different from all the others on your body. Research comparing the ugly duckling approach to the ABCDE rule found that everyday people using the ugly duckling method had significantly higher accuracy in identifying melanoma, with 100% sensitivity for detection. If a spot stands out as the odd one on your skin, that alone is a reason to have it evaluated.
Symptoms You Can Feel
Melanoma isn’t always painless. Some melanomas itch persistently, feel tender to the touch, or bleed without much provocation. A mole that starts to ooze, crust over, or bleed when it hasn’t been scratched or irritated is a red flag. So is a sore that simply won’t heal. These physical sensations tend to appear as a melanoma grows thicker, so they often indicate a more advanced lesion, but they can also be the first thing a person notices.
Melanoma That Doesn’t Look Like Melanoma
About 5% of melanomas are “amelanotic,” meaning they lack the dark pigment most people associate with skin cancer. Instead, they appear as a pink, red, or skin-toned bump or patch. Because they don’t fit the classic image of a dark, irregular mole, amelanotic melanomas are frequently mistaken for a pimple, a bug bite, or a harmless skin irritation. This confusion means they’re often diagnosed at a later stage than pigmented melanomas. If you have a pink or reddish spot that persists for weeks without healing, especially if it’s firm or raised, it deserves a closer look.
Melanoma Under the Nails
Subungual melanoma develops beneath a fingernail or toenail. The hallmark sign is a dark, vertical stripe running the length of the nail. A single stripe is typically less than 3 millimeters wide at first but gradually widens over time. Another key warning sign, known as the Hutchinson sign, is when the dark pigment spreads beyond the nail itself onto the surrounding skin of the cuticle or fingertip. The nail may also become brittle, crack, or partially separate from the nail bed.
This type falls under a broader category called acral lentiginous melanoma, which also includes melanomas on the palms of the hands and soles of the feet. It’s the most common form of melanoma in people with darker skin tones, and because these locations aren’t typically checked during casual self-exams, it’s frequently caught late.
Melanoma in the Eyes
Eye melanoma develops in the pigment-producing cells inside the eye and sometimes causes no symptoms at all, getting discovered only during a routine eye exam. When symptoms do appear, they include floaters or specks of dust drifting across your vision, flashes of light, a growing dark spot on the colored part of the eye (the iris), a change in the shape of the pupil, blurry vision in one eye, or loss of side vision. These symptoms overlap with other, less serious eye conditions, but a dark spot on the iris that’s growing is particularly distinctive.
Melanoma Inside the Body
Mucosal melanoma develops on the moist tissue lining internal surfaces of the body. It’s rare, but its symptoms are easy to dismiss as something minor.
In the mouth, it can show up as a lump on the tongue that keeps growing, a sore that won’t heal, unexplained bleeding, mouth pain, or dentures that suddenly stop fitting properly. In the nasal passages, the most common signs are repeated nosebleeds from one nostril, a feeling of something stuck in the nose, a continuous runny nose, or facial pain. In the anorectal area, symptoms include rectal pain, a lump or mass near the anus, bleeding, constipation, or persistent itching.
Because none of these symptoms scream “skin cancer,” mucosal melanoma is frequently misdiagnosed as an infection, a polyp, or hemorrhoids before the correct diagnosis is made. The key pattern to watch for is a symptom that’s one-sided (like nosebleeds only from one nostril) or a lesion that grows steadily instead of resolving on its own.
Who Needs to Check and How Often
Everyone benefits from a monthly self-exam, but the stakes are higher if you have fair skin, a history of sunburns, many moles (especially 50 or more), or a family history of melanoma. A good self-exam covers your entire body, including areas that rarely see the sun: the scalp, between the toes, the soles of your feet, under your nails, and your back. Use a hand mirror or ask a partner for help with hard-to-see spots.
Take photos of moles that concern you. Comparing images over a few months makes it much easier to spot subtle changes in size, shape, or color than relying on memory alone. If anything on your skin fits the ABCDE criteria, stands out as an ugly duckling, or simply looks different than it did a few months ago, a dermatologist can evaluate it with a dermoscope and, if needed, take a biopsy to rule out melanoma. Early-stage melanomas are typically removed with a simple outpatient procedure and carry an excellent prognosis.