Skin cancer usually announces itself as a visible change on your skin: a new spot that looks different from everything around it, or an existing mole that starts shifting in color, shape, or size. The tricky part is that skin cancer doesn’t always look dramatic. It can resemble a pimple that won’t heal, a shiny bump, a dark streak under a fingernail, or a flat scaly patch you barely notice. Knowing what to look for across the three main types gives you the best chance of catching it early, when treatment is simplest.
The ABCDE Rule for Melanoma
Melanoma is the most dangerous form of skin cancer, with an estimated 112,000 new cases expected in the U.S. in 2026 alone. The standard method for spotting it at home is the ABCDE checklist:
- Asymmetry: One half of the mole doesn’t match the other. Normal moles are roughly symmetrical.
- Border: The edges look ragged, notched, or blurred rather than smooth and well-defined. Pigment may seem to spread into surrounding skin.
- Color: Instead of a single uniform shade, you see a mix of brown, tan, black, or even patches of white, gray, red, pink, or blue within the same spot.
- Diameter: The spot is larger than about 6 millimeters (roughly the size of a pencil eraser), though melanomas can sometimes be smaller.
- Evolving: The mole has visibly changed over weeks or months in size, shape, color, or how it feels.
Not every melanoma will check all five boxes. A mole that only meets one or two criteria, especially “E” for evolving, still deserves a closer look from a dermatologist.
The Ugly Duckling Sign
Most of your moles tend to look like each other. They share a general color, size, and shape that’s “normal for you.” The ugly duckling sign is a simple concept: if one spot stands out from the rest, it’s suspicious. That outlier might be darker, lighter, larger, or smaller than its neighbors. Even a mole that sits alone on a stretch of skin with nothing to compare it to counts as an ugly duckling. This approach catches melanomas that don’t neatly fit the ABCDE criteria because it relies on pattern recognition rather than a checklist.
Nodular Melanoma and the EFG Rule
One subtype of melanoma doesn’t play by the usual rules. Nodular melanoma often grows as a round, symmetrical bump, so it can pass the ABCDE test and still be dangerous. It tends to grow downward into the skin rather than spreading outward, which makes it more aggressive. For raised spots, use the EFG rule instead:
- Elevated: The lesion is raised above the skin surface.
- Firm: It feels solid to the touch, not soft or squishy.
- Growing: It’s getting bigger over weeks or months.
Any firm, raised bump that keeps growing, especially one that’s dark or bleeds easily, should be evaluated promptly.
What Basal Cell Carcinoma Looks Like
Basal cell carcinoma is the most common skin cancer and typically the least aggressive, but it can cause serious damage to surrounding tissue if left alone. It shows up most often on sun-exposed areas like the face, ears, and neck. The appearance varies more than people expect:
- A shiny, slightly translucent bump that looks pearly white or pink. You might notice tiny blood vessels running through it.
- A brown, black, or blue spot with a slightly raised, see-through border.
- A flat, scaly patch that slowly grows larger over time.
- A white, waxy, scar-like area with no clear edges, sometimes appearing without any prior injury to that spot.
- A sore that bleeds, scabs over, heals partially, then opens up again.
On darker skin, basal cell carcinoma is more likely to appear as a brown or black bump with a translucent border, which can make it harder to recognize. The hallmark clue across all skin tones is a sore that repeatedly breaks open or simply never fully heals.
What Squamous Cell Carcinoma Looks Like
Squamous cell carcinoma is the second most common skin cancer. It tends to appear on chronically sun-exposed skin, but it can also develop on the lips, inside the mouth, and on the genitals. Watch for:
- A firm bump (nodule) that may be skin-colored, pink, red, brown, or black depending on your skin tone.
- A flat sore topped with a scaly, crusty surface.
- A new sore or raised area forming on an old scar.
- A rough, scaly patch on the lip that may become an open sore.
- A wart-like growth that doesn’t go away.
A useful rule of thumb: any sore or scab that hasn’t healed within about two months warrants a professional evaluation. The same goes for a flat, scaly patch that persists no matter what you do.
Skin Cancer on Palms, Soles, and Nails
Acral lentiginous melanoma develops in places most people never think to check: the palms of the hands, the soles of the feet, and under fingernails or toenails. It accounts for a small percentage of melanomas overall, but it’s the most common type in people with darker skin tones, partly because other forms of melanoma (which are linked to UV exposure on lighter skin) are less frequent in this group.
On the palms or soles, it typically appears as an unevenly pigmented brown or black spot that looks different from the surrounding skin and grows over time. Under a nail, it often shows up as a dark streak or band of color running from the cuticle to the tip. People frequently mistake it for a bruise, blood blister, or wart, which delays diagnosis. By the time it starts bleeding or becomes painful to walk on, it may have progressed significantly.
A helpful mnemonic for these spots is CUBED: Colored lesion, Uncertain diagnosis, Bleeding, Enlargement, and Delay in healing. If any of those apply to a spot on your hands, feet, or nails, get it checked.
How to Do a Full Self-Exam
A thorough self-check takes about 10 minutes and works best with a full-length mirror, a hand mirror, and good lighting. Work through your body systematically so you don’t skip anything:
Start with your face, ears, and neck, then check your scalp using the hand mirror and a comb to part your hair section by section. Move to your chest and torso, then examine both arms: the tops, undersides, and the often-missed backs of your upper arms. Check the tops and palms of your hands, including between your fingers and around each nail.
Use the full-length mirror to look at your back, buttocks, and the backs of your legs. Examine your genital area. Finally, sit down and check the tops and soles of your feet, between every toe, and around the toenails.
The goal isn’t to diagnose anything yourself. It’s to build a mental map of what your skin normally looks like so you notice when something changes. Doing this once a month makes new or evolving spots much easier to catch.
What Happens if Something Looks Suspicious
When a dermatologist evaluates a concerning spot, they’ll typically examine it with a dermatoscope, a handheld magnifying tool with its own light source. This allows them to see structures in the skin invisible to the naked eye, and research published in The Lancet Oncology found it improves diagnostic accuracy for melanoma by 49% compared to looking without one.
If the spot still looks concerning under magnification, the next step is a biopsy, where a small sample of skin is removed and examined under a microscope. For spots suspicious for melanoma, the standard approach is to remove the entire lesion with a small margin of normal skin around it. This gives the pathologist the complete picture, including how deep the abnormal cells go, which is critical for determining the stage. For spots that are more likely a basal or squamous cell carcinoma, a partial sample (removing just the surface or a small plug of tissue) is often sufficient.
A biopsy is a quick, in-office procedure done under local numbing. Results typically come back within one to two weeks. If the biopsy confirms cancer, treatment options and next steps depend entirely on the type and how deep it has grown, which is why early detection, when a cancer is still thin and superficial, makes such a significant difference in outcomes.