Skin cancer shows up as a visible change on your skin: a new spot, a mole that looks different than it used to, or a sore that won’t heal. The specific warning signs depend on which type of skin cancer is involved, but the core skill is the same. You’re looking for anything on your skin that is new, changing, or unusual compared to everything around it.
There’s no way to diagnose skin cancer at home. Only a biopsy, where a small sample of skin is removed and examined under a microscope, can confirm it. But knowing what to look for helps you catch something early, when treatment is simplest and most effective.
Warning Signs of Melanoma
Melanoma is the most dangerous form of skin cancer, but it’s also the one with the clearest visual checklist. Dermatologists use what’s called the ABCDE rule to flag suspicious moles:
- Asymmetry: One half of the mole doesn’t match the other half.
- Border: The edges are ragged, notched, or blurred rather than smooth. Pigment may spread into surrounding skin.
- Color: Multiple shades are present, such as brown, tan, and black mixed together. You might also see patches of white, gray, red, pink, or blue.
- Diameter: The spot is larger than about 6 millimeters, roughly the size of a pencil eraser. Melanomas can be smaller, but most exceed this threshold.
- Evolving: The mole has changed in size, shape, color, or height over the past few weeks or months. New symptoms like itching, bleeding, or scabbing also count.
You don’t need all five features to be concerned. Even one, especially “evolving,” is worth getting checked. A mole that looked the same for years and suddenly starts changing deserves attention regardless of its size or symmetry.
There’s also what dermatologists call the “ugly duckling” sign. If you have many freckles or moles and one of them looks noticeably different from all the others, that outlier is worth examining. It might be larger, darker, more raised, or scabbed over. The idea is simple: your moles tend to look like each other, and the one that doesn’t fit the pattern could be a problem.
What Basal Cell Carcinoma Looks Like
Basal cell carcinoma is the most common skin cancer, and it looks quite different from melanoma. The classic sign is a shiny, slightly translucent bump, sometimes described as “pearly.” On lighter skin it appears white or pink. On brown or Black skin it often looks brown or glossy black. You might notice tiny blood vessels running through it. These bumps tend to bleed easily and then scab over, sometimes repeatedly.
Not all basal cell carcinomas are bumps, though. Some appear as flat, white, waxy patches that resemble a scar, with no clearly defined border. Others look like open sores that heal partially, then reopen. The defining feature across all of these is persistence: the spot doesn’t go away on its own, and it may slowly grow over months.
What Squamous Cell Carcinoma Looks Like
Squamous cell carcinoma, the second most common type, often starts in areas that get a lot of sun exposure: the face, ears, hands, and forearms. It can appear as a firm bump or nodule that may be skin-colored, pink, red, brown, or black depending on your skin tone. It can also show up as a flat sore with a scaly, crusty surface.
A rough, scaly patch on your lip that develops into an open sore is a particularly characteristic presentation. Squamous cell carcinoma can also appear as a new raised area on an old scar, or as a wart-like growth. Sores or rough patches inside the mouth also fall into this category. Like basal cell carcinoma, the key pattern is a spot that persists, grows, or won’t fully heal.
Skin Cancer on Darker Skin
Skin cancer looks and behaves differently in people with darker skin tones. The type of particular concern is acral lentiginous melanoma, which develops on the palms, soles of the feet, and under fingernails or toenails. These are areas that don’t get much sun exposure, so people often don’t think to check them.
On the palms or soles, this cancer typically appears as an unevenly pigmented black or brown spot that looks different from the surrounding skin and grows over time. Under a nail, it shows up as a dark streak or band of color running from the cuticle to the tip. The standard ABCDE rule doesn’t apply well here. Instead, specialists at MD Anderson Cancer Center use the acronym CUBED: Colored lesion, Uncertain diagnosis, Bleeding, Enlargement, and Delay in healing.
One of the biggest problems with this type of melanoma is that people delay getting it checked. Many patients assume the spot is just a bruise, a blood blister, or a wart. By the time it starts bleeding or causing pain while walking, it may have progressed significantly. If you notice a dark spot on your palm, sole, or under a nail that doesn’t resolve within a few weeks, that’s worth showing to a dermatologist.
How to Check Your Own Skin
The American Academy of Dermatology recommends a systematic head-to-toe approach so you don’t miss anything. You’ll need a full-length mirror and a hand mirror, and good lighting.
Start by standing in front of the full-length mirror and looking at your body from the front and back, then raise your arms and check both sides. Bend your elbows and examine your forearms, underarms, fingernails, and palms carefully. Then sit down and check the backs of your legs, the tops and soles of your feet, the spaces between your toes, and your toenails. Use the hand mirror to examine the back of your neck and your scalp, parting your hair as you go. Finally, use it to check your back and buttocks.
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 is a reasonable frequency. If you have a partner, ask them to help with areas you can’t easily see.
Spots That Mimic Skin Cancer
Not every suspicious-looking spot turns out to be cancerous. Seborrheic keratoses, for example, are extremely common harmless growths that can look dark, raised, and irregular enough to cause alarm. They often have a waxy, “stuck-on” appearance and may contain tiny white cyst-like dots or pore-like openings visible on close inspection. Melanomas don’t have these features. Age spots, cherry angiomas (small red dots), and dermatofibromas (firm, pea-sized bumps) are other benign growths that people sometimes worry about.
The problem is that even experienced dermatologists sometimes can’t tell the difference by eye alone. That’s why the threshold for getting something checked should be low. If a spot is new, changing, or just looks “off” to you, a quick visit to a dermatologist is far better than months of watching and wondering.
What Happens at the Dermatologist
A dermatologist will first examine the spot visually, often using a dermatoscope, which is essentially a magnifying lens with a light that reveals structures beneath the skin’s surface invisible to the naked eye. If the spot looks suspicious, they’ll perform a biopsy.
For suspected basal cell or squamous cell carcinoma, the most common approach is a shave biopsy, where a thin layer is sliced from the top of the lesion with a blade, or a punch biopsy, which uses a small circular tool to remove a deeper core of tissue. Both are done with local anesthesia in the office and take just a few minutes. For suspected melanoma, an excisional biopsy is preferred, meaning the entire spot plus a small margin of surrounding skin is removed with a scalpel. This ensures the lab has enough tissue to measure how deep the melanoma extends, which is the single most important factor in determining how serious it is.
Results typically come back within one to two weeks. If the biopsy confirms cancer, your next steps depend entirely on the type and how advanced it is. Caught early, all three common skin cancers have high cure rates, which is the whole point of learning to spot them.