Skin cancer shows up in several distinct ways depending on the type, but the general rule is simple: look for any spot on your skin that is new, changing, or different from everything around it. Early detection matters enormously. When melanoma is caught while still localized, the five-year survival rate is about 98%. Once it has spread to distant parts of the body, that drops to roughly 16%.
The ABCDE Rule for Melanoma
Melanoma is the most dangerous form of skin cancer, but it’s also one of the easiest to screen for at home using five visual features:
- Asymmetry: One half of the mole doesn’t match the other half.
- Border: The edges are ragged, notched, or blurred. Pigment may spread into the surrounding skin.
- Color: The spot isn’t one uniform shade. You might see a mix of brown, tan, and black, sometimes with patches of white, gray, red, pink, or blue.
- Diameter: The spot is larger than 6 millimeters across, roughly the size of a pencil eraser. Melanomas can be smaller than this, but most exceed that threshold.
- Evolving: The mole has changed in size, shape, or color over the past few weeks or months.
Not every melanoma will check all five boxes, and some are small or light-colored in their earliest stages. The single most important factor is change. A mole that looked the same for years and is now shifting in any way deserves a closer look.
The “Ugly Duckling” Sign
Beyond examining each mole individually, dermatologists use what’s called the “ugly duckling” approach. Instead of evaluating one spot in isolation, you compare it to all the other moles on your body. Most of your moles will share a general family resemblance in color, size, and shape. The one that looks nothing like the rest, the outlier, is the one to pay attention to. This method is especially useful for catching melanomas that don’t obviously meet the ABCDE criteria but still stand out when viewed alongside your other spots.
Basal Cell Carcinoma
Basal cell carcinoma is the most common skin cancer. It grows slowly and rarely spreads to other organs, but it can cause significant damage to surrounding tissue if left untreated. Its appearance varies with skin tone.
On lighter skin, it often shows up as a shiny, slightly translucent bump that looks pearly white or pink. You may notice tiny blood vessels running through or around the bump. On brown and Black skin, basal cell carcinoma typically appears as a brown or glossy black bump with a rolled border, and those small blood vessels can be harder to spot.
Other forms include flat, white, waxy patches that resemble a scar without a clearly defined edge. In any form, the hallmark is a sore that bleeds, scabs over, and then reopens. A spot that won’t fully heal is one of the most reliable warning signs for this type of cancer.
Squamous Cell Carcinoma
Squamous cell carcinoma is the second most common type. It tends to appear in areas that get a lot of sun exposure, like the face, ears, hands, and lips, but it can develop anywhere on the body.
Common presentations include a firm bump (nodule) that may be skin-colored, pink, red, brown, or black depending on your complexion. It can also look like a flat sore with a scaly, crusty surface, or a rough patch on the lip that eventually becomes an open sore. Sometimes it appears as a raised, wartlike growth. A new sore or raised area developing on top of an old scar is another red flag. Squamous cell carcinoma can also develop inside the mouth, appearing as a rough patch or sore that doesn’t resolve.
Skin Cancer on Darker Skin Tones
While overall skin cancer rates are lower in people with darker skin, one type occurs equally across all races and backgrounds: acral lentiginous melanoma. This form accounts for the majority of melanoma cases in people of color, and it shows up in places most people don’t think to check.
The main sign is a black or brown discoloration on the sole of the foot or the palm of the hand. It can look like a bruise or stain at first, but it grows in size over time. A subtype called subungual melanoma develops under fingernails or toenails, appearing as dark vertical streaks running along the nail bed. It’s often mistaken for a fungal infection or dried blood. As it progresses, the nail may crack or break. Because these locations are easy to overlook, melanoma in people of color is frequently diagnosed at a later, more advanced stage.
Merkel Cell Carcinoma
Merkel cell carcinoma is rare but aggressive. It typically appears as a firm, painless, red or pink bump on sun-exposed skin. The features that help identify it can be remembered with the acronym AEIOU: asymptomatic (not tender), expanding rapidly, immune suppression in the patient, older than 50, and ultraviolet-exposed or fair skin. In a study of 195 cases, 89% of Merkel cell tumors had three or more of these features. The combination that should raise the most concern is a red bump that’s growing fast yet doesn’t hurt. Roughly 63% of these tumors had grown noticeably in the three months before diagnosis, and 88% were completely painless despite that rapid growth.
How to Do a Full-Body Skin Check
A monthly self-exam is one of the most effective ways to catch skin cancer early. The best time to do it is right after a shower, when your skin is bare and well-lit. You’ll need a full-length mirror, a hand mirror, and a comb.
Start by standing in front of the full-length mirror and looking at your entire body, front and back. Raise your arms and check both sides of each arm, including the backs of your upper arms, which are easy to miss. Bend your elbows and inspect both sides of your forearms. Look at the tops and palms of your hands. Check your face, neck, and the back of your neck. Use the hand mirror and comb together to part your hair and examine your scalp section by section.
Move down to the front and back of both legs. Look at your buttocks, between your buttocks, and your genital area. Finally, sit down and examine your feet, including the soles and the spaces between your toes. For hard-to-see areas like your back and the back of your scalp, ask someone you trust to help. Taking photos of spots you want to track can make it easier to notice changes month to month.
What Deserves a Professional Look
Any mole or growth that meets one or more of the ABCDE criteria should be evaluated by a dermatologist. The same goes for any spot that stands out as an ugly duckling compared to the rest of your moles. Open sores that won’t heal are one of the clearest signals that a biopsy may be needed. A lesion that repeatedly bleeds, crusts, and fails to close is not just a stubborn wound. New growths that appear suddenly, especially firm or shiny bumps, also warrant evaluation. And dark streaks under a nail that can’t be explained by injury should not be dismissed as bruising or fungus without a professional assessment.