Skin cancer often shows up as a new or changing spot that looks different from the rest of your skin. The tricky part is that it doesn’t always look dramatic. Some skin cancers resemble a pimple that won’t heal, a shiny bump, or a rough patch you keep scratching. Knowing what to look for, and where to look, makes a real difference in catching it early.
The ABCDE Rule for Melanoma
Melanoma is the most dangerous form of skin cancer, but it’s also the one with the clearest visual warning signs. Dermatologists use a five-part checklist called the ABCDE rule to evaluate suspicious moles:
- Asymmetry: One half of the mole doesn’t match the other in shape or size.
- Border: The edges are ragged, notched, or blurred rather than smooth. Pigment may spread into the surrounding skin.
- Color: Instead of one uniform shade, the mole contains a mix of brown, black, tan, white, gray, red, pink, or blue.
- Diameter: Most melanomas are larger than 6 millimeters across (about the size of a pencil eraser), though they can be smaller.
- Evolving: The mole has changed in size, shape, color, or height over weeks or months, or you notice new symptoms like itching or scabbing.
You don’t need all five features to be concerned. Even one, especially “evolving,” is enough to warrant a closer look from a dermatologist.
The Ugly Duckling Sign
The ABCDE rule evaluates individual moles, but there’s another approach that works by comparison. Most of your moles tend to look like each other in color, size, and shape. The “ugly duckling” is the one that stands out from the rest. It could be larger, darker, lighter, or just shaped differently than its neighbors. An isolated mole with no similar-looking moles nearby also counts as an ugly duckling. This is a simple but surprisingly effective way to flag spots you might otherwise overlook.
What Non-Melanoma Skin Cancer Looks Like
Melanoma gets the most attention, but basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) are far more common. They look quite different from melanoma, and from each other.
Basal Cell Carcinoma
BCC typically shows up on sun-exposed areas like the face, head, neck, and arms, though it can appear anywhere. On lighter skin, it often looks like a small, shiny, pearly bump that may have a pink or translucent quality. Sometimes it appears as a flat, pale area that resembles a scar, or a pink growth with raised edges and visible blood vessels spreading outward from the center. One of the most telling signs is a sore that oozes, crusts over, and never fully heals, or heals and then returns. On darker skin, BCC shares many of the same features (translucent, shiny, raised edges) but tends to be darker in color.
Squamous Cell Carcinoma
SCC also favors sun-exposed skin in lighter-skinned people, commonly the face, ears, neck, lips, and backs of the hands. In people with darker skin, SCC is more likely to appear in areas that don’t get much sun. It often presents as a rough, scaly red or dark patch that may crust or bleed, a raised lump sometimes with a dip in the center, or a wart-like growth. Like BCC, a sore that won’t stay healed is a hallmark.
Both types can also appear as a flat area with only subtle changes from normal skin, which is why regular self-checks matter even if you’re not seeing anything obviously alarming.
Precancerous Spots to Watch
Not every worrisome spot is cancer yet. Actinic keratoses are rough, dry, scaly patches caused by years of sun exposure. They’re usually smaller than an inch across, range from pink to red to brown, and tend to appear on the head, neck, hands, and forearms. Some itch, burn, or bleed. Left untreated, roughly 5% to 10% of actinic keratoses eventually develop into squamous cell carcinoma. If you feel a persistently rough patch on sun-exposed skin, especially one that bleeds or crusts, it’s worth getting checked even if it doesn’t look like much.
Skin Cancer on Darker Skin
There’s a widespread misconception that people with darker skin don’t get skin cancer. They do, and certain types are disproportionately dangerous because they’re caught later. Acral lentiginous melanoma occurs at equal rates across all races and accounts for the majority of melanoma diagnoses in people of color. It doesn’t appear in the typical sun-exposed spots. Instead, it develops on the palms of the hands, soles of the feet, and under fingernails or toenails.
On the palms or soles, it starts as a dark brown or black discoloration that may look like a bruise or stain, then gradually grows. Under nails, it appears as dark vertical streaks running along the nail bed and can be mistaken for a fungal infection or blood under the nail. As it progresses, it may cause the nail to crack or break. These hidden locations make self-examination of your hands, feet, and nails especially important.
How to Do a Skin Self-Exam
A thorough self-check takes about 10 minutes and should cover your entire body. You’ll need a full-length mirror, a hand mirror, and a comb. Work systematically so you don’t skip areas:
- Front and back: Stand in front of a full-length mirror and examine your entire torso, both sides.
- Arms: Raise your arms and check your underarms, then both sides of each arm, including the backs of your upper arms.
- Hands: Look at the tops and palms, including between your fingers.
- Legs: Examine the front and back of both legs.
- Feet: Check the soles, the tops, and the spaces between your toes.
- Buttocks and genital area: Use a hand mirror to check areas that are difficult to see directly.
- Scalp, face, and neck: Use a comb to part your hair section by section while holding a hand mirror. Check behind your ears and the back of your neck.
If you do this monthly, you’ll develop a mental map of what’s normal for your body. That baseline makes it much easier to notice when something changes. Taking photos of spots you want to track can help you compare over time.
What Happens if You Find Something Suspicious
A dermatologist can evaluate a suspicious spot visually, often using a dermatoscope (a handheld magnifying device with a light) for a closer look. If anything raises concern, the next step is a biopsy, where a small sample of skin is removed and examined under a microscope. This is the only way to confirm whether a spot is cancerous.
There are a few common biopsy approaches. A shave biopsy removes a thin surface layer with a razor blade. A punch biopsy takes a small, round, deeper sample. An excisional biopsy uses a scalpel to remove a larger area of skin, sometimes the entire lesion. All three are done with local numbing and take just minutes. Your dermatologist will choose the method based on the size, location, and depth of the spot in question.
The key signal to act on is change. A mole that shifts in color, size, or texture. A sore that bleeds, crusts, and won’t heal. A new spot that doesn’t look like anything else on your body. A dark streak under a nail that keeps growing. None of these are guaranteed to be cancer, but all of them are worth showing to a professional rather than watching and waiting.