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 within two weeks. The specific signs depend on which type of skin cancer is developing, but the core skill is the same. You’re looking for anything new, changing, or unusual compared to the rest of your skin. About 6.1 million adults in the U.S. are treated for non-melanoma skin cancers each year, making this the most common cancer by far.
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-letter checklist called the ABCDE rule to evaluate moles and dark spots:
- Asymmetry: One half of the mole doesn’t match the other half in shape.
- Border: The edges are ragged, notched, or blurred rather than smooth and round. Pigment may spread into the surrounding skin.
- Color: The color is uneven. You might see shades of brown, black, and tan mixed together, or 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 changed in size, shape, or color over the past few weeks or months.
You don’t need all five features to be concerned. A single one, especially “evolving,” is enough to warrant a closer look from a dermatologist. A useful companion to the ABCDE rule is the “ugly duckling” sign: if one mole looks noticeably different from all the others on your body, that’s the one to pay attention to.
What Basal Cell Carcinoma Looks Like
Basal cell carcinoma is the most common type of skin cancer. It grows slowly and rarely spreads to other parts of the body, but it can damage surrounding tissue if left alone. It typically appears on sun-exposed areas like the face, ears, neck, and arms.
The classic sign is a shiny, slightly translucent bump that looks pearly white or pink on lighter skin. On brown or Black skin, the same bump often appears brown or glossy black. Tiny blood vessels may be visible on the surface, and the bump may bleed and then scab over repeatedly. Other forms include a flat, scaly patch that grows slowly over time, or a white, waxy, scar-like area without a clear border. A brown, black, or blue lesion with a slightly raised, translucent edge is another variant.
The hallmark across all these appearances is a sore or growth that doesn’t fully heal. It may scab, seem to improve, then open up again.
What Squamous Cell Carcinoma Looks Like
Squamous cell carcinoma is the second most common skin cancer. It’s more aggressive than basal cell carcinoma and can spread if not treated, though it’s still highly treatable when caught early. Look for a firm bump or nodule that may be skin-colored, pink, red, brown, or black depending on your skin tone. A flat sore with a scaly, crusty surface is another common presentation.
This type can also show up as a new raised area on an old scar, a rough scaly patch on the lip that becomes an open sore, or a sore or rough patch inside the mouth. Squamous cell carcinoma tends to develop on skin that gets regular sun exposure, but it can appear anywhere, including areas that rarely see sunlight.
Skin Cancer on Darker Skin Tones
Skin cancer is less common in people with darker skin, but it’s often diagnosed later because the signs are harder to spot and less widely recognized. One particularly important type is acral lentiginous melanoma, which develops exclusively on the palms of the hands, the soles of the feet, or under the nails. It affects people of all skin tones but makes up a larger proportion of melanoma cases in Black, Hispanic, and Asian patients.
On the palm or sole, it typically appears as an unevenly pigmented brown or black spot that looks different from the rest of your skin and grows over time. Under a fingernail or toenail, it may appear as a dark streak or band of color growing from the cuticle toward the tip of the nail. People commonly mistake it for a bruise, blood blister, or wart, which delays diagnosis. A helpful screening tool for these spots uses the acronym CUBED: Colored lesion, Uncertain diagnosis, Bleeding, Enlargement, and Delay in healing.
Signs You Can Feel, Not Just See
Skin cancer isn’t always just a visual change. A spot that persistently itches, feels tender, or causes pain deserves attention. A sore that heals and then reopens, or one that bleeds with minimal contact, is another warning sign. These sensory symptoms can show up with any type of skin cancer and sometimes appear before the visual changes become obvious.
How to Check Your Own Skin
A monthly self-exam is the standard recommendation. You’ll need a full-length mirror, a hand mirror, and good lighting. Start with your face, ears, and neck, then work down your arms, checking the tops and undersides of both. Look at your chest and torso, then use the hand mirror to examine your upper and lower back, buttocks, and genital area.
For your legs, check the fronts and backs of your thighs, shins, and calves. Use the hand mirror to see the bottoms of your feet, including between your toes. Part your hair with a comb or blow dryer to check your scalp section by section. Ask a partner or family member to help with areas you can’t see well, like your back and the back of your neck.
The goal isn’t to diagnose anything yourself. It’s to build a mental map of your skin so that when something changes, you notice it quickly. Taking photos of moles you want to track can make it easier to spot subtle changes month to month.
What Happens if Something Looks Suspicious
Any new or changing spot that persists for two weeks or more is worth having a doctor examine. The same goes for a sore that won’t heal, a spot that itches, hurts, or bleeds, or a mole that looks very different from others on your body.
If your doctor thinks a spot needs further evaluation, the next step is a biopsy, which means removing a small sample of skin to examine under a microscope. There are a few common methods. A shave biopsy uses a thin blade to remove a superficial layer, usually without stitches. A punch biopsy uses a small circular tool to take a deeper sample, and an excisional biopsy removes the entire suspicious area with a scalpel. Both punch and excisional biopsies typically require a couple of stitches. The procedure is done under local anesthesia, and results usually come back within one to two weeks.
Why Early Detection Matters
The survival gap between early and late-stage skin cancer is enormous. Melanoma caught while it’s still localized to the skin has a five-year survival rate of 97.6%. Once it spreads to nearby lymph nodes, that drops to 60.3%. If it reaches distant organs, the rate falls to 16.2%. Basal cell and squamous cell carcinomas have even better outcomes when caught early, with cure rates above 95% for localized tumors.
The difference between these outcomes often comes down to whether someone noticed a spot and acted on it. A monthly skin check takes about ten minutes, and knowing what to look for turns it from a vague exercise into something genuinely useful.