The classic warning signs of melanoma follow the ABCDE rule: a mole that is asymmetrical, has irregular borders, contains multiple colors, is larger than 6 millimeters (about the size of a pencil eraser), or is evolving over time. But melanoma doesn’t always play by those rules. Some forms skip the dark pigment entirely, others grow in places you’d never think to check, and a few look nothing like a typical mole. Knowing the full range of warning signs gives you a real advantage in catching this cancer early.
The ABCDE Rule
The ABCDE criteria, developed by the National Cancer Institute, remain the most widely used framework for spotting suspicious moles. Each letter flags a specific visual feature:
- Asymmetry. One half of the mole doesn’t match the other. Normal moles tend to be roughly symmetrical.
- Border. The edges are ragged, notched, or blurred rather than smooth. Pigment may spread into the surrounding skin.
- Color. The mole contains uneven shades of black, brown, or tan. You may also see patches of white, gray, red, pink, or blue within the same lesion.
- Diameter. The mole is wider than about 1/4 inch (6 mm), roughly the width of a pencil eraser. That said, any mole that seems to be growing deserves attention even if it’s still smaller than that threshold.
- Evolving. The mole has changed in size, shape, color, or texture over the past few weeks or months. Any noticeable shift is worth investigating.
No single feature on its own confirms melanoma, but the more of these characteristics a spot has, the more reason to get it evaluated. A mole that checks just one box, especially “E” for evolving, is still worth a closer look.
The Ugly Duckling Sign
The ABCDE rule evaluates each mole individually. The ugly duckling sign takes a different approach: it compares a mole to its neighbors. Most of your moles share a general “family resemblance” in color, size, and shape. If one mole stands out from the rest, looking clearly different from every other spot on your body, that outlier deserves attention. This method is especially useful for people with many moles, where it can be hard to evaluate each one in isolation.
Physical Symptoms Beyond Appearance
Melanoma isn’t always just a visual change. Some lesions produce physical sensations that serve as additional red flags. Itching in a mole that never itched before, new tenderness or pain, and spontaneous bleeding or oozing are all symptoms that warrant a professional evaluation. A mole that becomes inflamed, develops a crust, or won’t heal after minor irritation is behaving differently from a benign spot.
These symptoms sometimes appear before the visual changes become obvious, which makes paying attention to how a mole feels just as important as how it looks.
Nodular Melanoma: When ABCDE Falls Short
Not every melanoma grows outward in a flat, spreading pattern. Nodular melanoma grows vertically into the skin and often lacks the classic ABCDE features. It can appear symmetrical, have smooth borders, and be a single uniform color. Because it doesn’t match the textbook description, it’s frequently missed.
For nodular melanoma, dermatologists use a separate set of criteria called EFG: elevated (raised above the skin surface), firm to the touch, and growing progressively for more than a month. A bump on your skin that meets those three criteria, particularly one that keeps getting larger week after week, should be checked promptly. Nodular melanomas tend to be more aggressive because they penetrate deeper into the skin faster than other types.
Melanoma That Doesn’t Look Dark
When most people picture melanoma, they imagine a dark brown or black spot. Amelanotic melanoma breaks that assumption entirely. It appears as a pink, red, or skin-colored lesion, sometimes resembling a pimple, bug bite, or scar. About 5 percent of all melanomas are amelanotic, according to Memorial Sloan Kettering Cancer Center.
Because these lesions lack the dark pigment people expect, they’re frequently overlooked or mistaken for harmless skin conditions. That delay in recognition means amelanotic melanoma is often diagnosed at a later stage than pigmented forms. If you have a pinkish or reddish spot that persists for weeks, doesn’t respond to typical treatments, or slowly grows, it’s worth having a dermatologist examine it.
Melanoma on Palms, Soles, and Under Nails
Acral lentiginous melanoma develops in places many people never think to check: the palms of the hands, soles of the feet, and beneath fingernails or toenails. It is the most common form of melanoma in people with darker skin tones, though it can occur in anyone.
The warning signs differ from what you’d look for elsewhere on the body. On the palms or soles, watch for a black, gray, tan, or brown spot with irregular borders, or a thick patch of skin that wasn’t there before. Reddish or pinkish lesions with uneven edges also occur. Under the nails, the hallmark sign is an unexplained dark streak running vertically across the nail bed. A changing or growing lesion on the hands or feet, or one that itches, bleeds, or becomes inflamed, is cause for concern.
These areas get less sun exposure, so people who are diligent about checking sun-exposed skin often skip them entirely. Make a habit of examining between your toes, the soles of your feet, and your nail beds during self-exams.
Hidden Locations You Might Miss
Melanoma can develop in places that never see sunlight and that you’re unlikely to monitor on your own. Mucosal melanoma grows on the moist tissue lining the inside of the body, including the nose, mouth, lips, anus, rectum, vagina, and vulva. Because these areas are hidden, symptoms often go unnoticed until the cancer is more advanced.
Signs of mucosal melanoma depend on location. In the nose or mouth, you might notice unexplained dark patches, persistent sores, or bleeding. In the anorectal or vulvovaginal regions, symptoms can include discoloration, a lump, pain, or bleeding that doesn’t have an obvious explanation. These are rare, but they’re a reminder that melanoma isn’t exclusively a problem on visible, sun-exposed skin.
The scalp is another commonly overlooked spot. Hair coverage makes it difficult to notice new or changing lesions. If your hairstylist or barber points out an unusual spot, take it seriously.
How to Do a Self-Exam
A thorough skin self-exam takes about 10 to 15 minutes and should cover your entire body. Use a full-length mirror and a hand mirror to check hard-to-see areas like your back, the backs of your legs, and your scalp. Part your hair in sections to expose the skin underneath. Check between your fingers and toes, the soles of your feet, your palms, and your nail beds.
The goal isn’t to diagnose anything yourself. It’s to notice change. Taking photos of moles you want to track makes it far easier to spot subtle shifts in size, shape, or color over months. When something looks different from your last check, or when a spot stands out from your other moles, that’s your cue to schedule an evaluation with a dermatologist. The frequency of professional skin exams depends on your individual risk factors, including your history of sun exposure, family history of melanoma, and the number of moles you have.