Malignant melanoma typically appears as a mole or spot on the skin that looks uneven in shape, has multiple colors, and changes over time. It can be flat or raised, and while most are darker than 6 millimeters wide (about the size of a pencil eraser) when diagnosed, melanomas can also be smaller, lighter, or even skin-colored. Knowing what to look for across the different forms this cancer takes is the key to catching it early.
The ABCDE Checklist
The most widely used framework for spotting melanoma is the ABCDE mnemonic, developed as a self-detection tool by dermatologists. Each letter describes a visual feature to watch for:
- Asymmetry: One half of the mole doesn’t match the other. A normal mole is roughly symmetrical; melanoma tends to grow unevenly.
- Border: The edges are ragged, notched, or blurred rather than smooth. The pigment may spread outward into surrounding skin, making the boundary hard to define.
- Color: Multiple shades appear within the same spot. You might see a mix of black, brown, and tan, along with areas of white, gray, red, pink, or blue.
- Diameter: Most melanomas are larger than 6 millimeters when first diagnosed, roughly the width of a pencil eraser. However, the American Academy of Dermatology now notes that melanomas can be smaller, so any new or growing spot deserves attention regardless of size.
- Evolving: The mole has changed in size, shape, or color over the past few weeks or months. New symptoms like itching, bleeding, or crusting also count as evolution.
Not every melanoma will check all five boxes. Some show only one or two of these features. The single most important sign is change: a spot that looked one way a month ago and looks different today.
The “Ugly Duckling” Sign
Beyond the ABCDE criteria, there’s a simpler visual test. Most of your moles tend to resemble each other in size, color, and shape. The “ugly duckling” sign means one mole among your others that clearly stands out and looks different. That outlier, the one that doesn’t match its neighbors, warrants a closer look even if it doesn’t tick every ABCDE box.
Superficial Spreading Melanoma
This is the most common form of melanoma and the type most people picture. It usually starts as a flat or slightly raised spot with uneven borders and color variations within the same lesion. You might see patches of brown alongside darker black areas, or lighter zones mixed in. It tends to grow outward across the skin surface before pushing deeper, which is why early detection matters so much. It can appear anywhere on the body but is most common on the trunk in men and the legs in women.
Nodular Melanoma
Nodular melanoma looks and behaves differently from the flat, spreading type. It presents as a firm, dome-shaped bump on the skin. Colors range from blue-black or dark brown to red, pink, or even your natural skin tone. The critical difference is how it grows: instead of spreading outward first, it pushes vertically, with most of the cancer sitting below the surface like an iceberg. Because of this growth pattern, nodular melanoma can become dangerous quickly. A new, firm bump that’s growing steadily over weeks, especially one that bleeds or doesn’t heal, should be evaluated promptly.
Melanoma That Doesn’t Look Dark
About 5 percent of melanomas are amelanotic, meaning they produce little or no pigment. These appear as pink, red, or skin-colored spots rather than the dark lesions most people associate with melanoma. Because they don’t look “cancerous” to the untrained eye, amelanotic melanomas are frequently mistaken for pimples, bug bites, or other harmless skin irritations. That confusion often leads to a later-stage diagnosis compared with brown, black, or blue melanomas. If you have a pinkish spot that persists for weeks, grows, or bleeds without a clear cause, it’s worth having checked.
Melanoma on Palms, Soles, and Nails
Acral lentiginous melanoma appears in places people rarely think to check: the palms of the hands, soles of the feet, and under fingernails or toenails. On the palm or sole, it typically looks like an unevenly pigmented black or brown spot that stands out from the surrounding skin and grows over time. People often dismiss it as a bruise, blood blister, or wart, which delays diagnosis until the spot starts bleeding or becomes painful to walk on.
Under the nail, melanoma usually shows up as a dark brown or black streak running from the cuticle to the tip. The streak can be irregular, with varying shades of blackish brown. A single colored line is often less than 3 millimeters wide initially but gets wider over time. One important sign is the Hutchinson sign, where the dark pigment spreads beyond the nail itself and stains the skin around the cuticle. This is a strong indicator that the streak is melanoma rather than a harmless pigment band.
The standard ABCDE checklist doesn’t apply well to these locations. Specialists instead use the CUBED acronym: Colored lesion, Uncertain diagnosis, Bleeding, Enlargement, and Delay in healing. This form of melanoma is particularly important for people with darker skin tones, where it accounts for a larger proportion of melanoma diagnoses overall.
Early vs. More Advanced Appearance
At its earliest stage (melanoma in situ, or Stage 0), the cancer cells haven’t pushed past the top layer of skin. Visually, early melanoma tends to be flatter with subtle color variation. As melanoma becomes invasive and grows deeper, certain features become more common: irregular dots or clusters of pigment within the lesion, a blue-white haze or veil over part of the spot, and visible tiny blood vessels. A milky reddish area within the mole also appears more frequently in invasive melanoma. These changes reflect the cancer actively building its own blood supply and pushing into deeper tissue.
The practical takeaway: a flat, slightly uneven spot with mild color variation can still be melanoma. You don’t need to wait until a mole looks dramatically alarming. The earlier the catch, the simpler the treatment and the better the outcome.
What Changes to Watch For
The most actionable thing you can do is learn what your skin normally looks like and notice when something shifts. Specific changes that matter include a mole that’s getting bigger, developing new colors, or losing its previously smooth border. Surface changes are also telling: a mole that was always flat and suddenly becomes raised, starts crusting or flaking, or bleeds without being scratched or bumped. New sensory symptoms like itching or tenderness in or around a mole also signal that something may be happening beneath the surface.
A brand-new spot that appears in adulthood and looks unusual from the start also counts. Melanoma doesn’t always develop from an existing mole. It can arise on previously clear skin as a new, pigmented, or unusual-looking growth.