The classic signs of melanoma follow the ABCDE rule: a mole or spot that is asymmetrical, has irregular borders, contains multiple colors, measures larger than 6 millimeters (about the size of a pencil eraser), or is evolving over time. But melanoma doesn’t always look like a dark, irregular mole. It can appear as a pink bump, a streak under your nail, or even a sore inside your mouth. Knowing the full range of warning signs gives you the best chance of catching it early, when the five-year survival rate sits above 97%.
The ABCDE Rule
This is the most widely used framework for spotting melanoma on skin. Each letter flags a visual feature worth paying attention to.
- 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 or bleed into the surrounding skin.
- Color. The color is uneven. You might see shades of brown, tan, and black mixed together, or patches of white, gray, red, pink, or blue within the same spot.
- Diameter. Most melanomas are larger than 6 millimeters wide, roughly the width of a pencil eraser. That said, melanomas can be tiny. 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. A spot that looked stable for years and suddenly starts shifting is more concerning than one that has always looked the same.
Sensory Changes That Matter
Melanoma isn’t always just a visual change. A mole or spot that starts itching persistently, feels tender, or bleeds without being scratched or injured is signaling something worth investigating. These symptoms can show up alongside the ABCDE features or on their own. Spontaneous bleeding or oozing from a flat or raised spot is particularly worth noting, since normal moles almost never do this.
The Ugly Duckling Sign
Most people’s moles share a general “family resemblance.” They tend to be similar in size, shape, and color. The ugly duckling sign is simple: look for the one mole that doesn’t match the others. It might be darker, larger, or just visually different from everything around it. This approach is especially useful for people with many moles, where checking every spot against the ABCDE criteria can feel overwhelming. The outlier is the one to get checked.
Nodular Melanoma Looks Different
Not all melanomas spread outward across the skin’s surface. Nodular melanoma grows downward into the skin, which makes it more aggressive and harder to catch with the standard ABCDE checklist. It often appears as a raised, dome-shaped bump rather than a flat, irregular mole. It can be dark brown, black, red, or even skin-colored.
For this type, dermatologists use the EFG rule: elevated (raised above the skin surface), firm (feels solid to the touch rather than soft or squishy), and growing (noticeably increasing in size over weeks or months). If you have a new bump that’s firm and growing steadily, that combination alone is reason to have it evaluated, regardless of its color.
Melanoma Without Dark Pigment
About 5% of melanomas are amelanotic, meaning they lack the dark pigment most people associate with skin cancer. These appear as pink, red, or skin-toned spots. They might look like a pimple that won’t heal, a small scar you don’t remember getting, or a vaguely irritated patch of skin. Because they don’t match the typical image of melanoma, amelanotic melanomas are frequently mistaken for harmless skin conditions and tend to be diagnosed at a later stage. If you have a pink or reddish spot that persists for several weeks without explanation, especially if it’s firm or growing, it deserves a closer look.
Melanoma Under the Nails
Subungual melanoma appears beneath a fingernail or toenail, most commonly on the thumb or big toe. The hallmark sign is a dark vertical streak running from the base of the nail to the tip. The streak is usually brown or black and doesn’t grow out or disappear the way a bruise under the nail eventually would.
A particularly important warning sign is called Hutchinson’s sign: the dark pigment extends beyond the nail itself and discolors the skin around the cuticle or nail fold. This spread of pigment into the surrounding skin strongly suggests melanoma rather than a benign cause. Subungual melanoma is more common in people with darker skin tones and can be easy to dismiss as a fungal infection or injury.
Melanoma in Hidden Locations
Melanoma can develop on mucous membranes, the moist tissue lining areas inside the body. These mucosal melanomas are rare but easy to miss because they occur in places you wouldn’t normally check for skin cancer.
Mouth and Lips
Signs include a lump on the tongue that persists or grows, a sore in the mouth that won’t heal, unexplained mouth pain or bleeding, or dentures that suddenly stop fitting properly.
Nose and Sinuses
Repeated nosebleeds from one nostril, a persistent feeling of something stuck in your nose, a continuous runny nose, or unexplained facial pain can all point to mucosal melanoma in the nasal passages.
Anorectal Area
A mass or lump in the anus or rectum, rectal bleeding, persistent pain, constipation, or itching that doesn’t resolve can indicate melanoma in this region. These symptoms overlap heavily with hemorrhoids and other common conditions, which is part of why anorectal melanoma is often caught late.
Vulva and Vagina
Vaginal bleeding between periods or after menopause, unusual or bloody discharge, a lump or growth on the vulva or vagina, or persistent itching that doesn’t respond to treatment are all potential signs.
Why Early Detection Changes Everything
The survival gap between early and late-stage melanoma is enormous. When melanoma is still localized to the skin and hasn’t spread, the five-year survival rate is 97.6%. Once it reaches nearby lymph nodes (regional spread), that drops to about 60%. If it spreads to distant organs, survival falls to roughly 16%. The same cancer caught at different times has a dramatically different outcome, which is what makes recognizing these signs so consequential.
Monthly self-checks give you the best shot at catching changes early. Pay attention to spots in places you might not think to look: the scalp, between your toes, on the soles of your feet, and under your nails. Use a mirror or ask a partner to check your back. The goal isn’t to diagnose yourself. It’s to notice something new, different, or changing, and then get a professional evaluation before the window of easy treatment closes.