The most common signs of skin cancer are new growths, sores that don’t heal, and existing moles or spots that change in size, shape, or color. What these signs look like depends on the type of skin cancer, and the three main types, basal cell carcinoma, squamous cell carcinoma, and melanoma, each show up differently on the skin.
Signs of Melanoma
Melanoma is the most dangerous form of skin cancer, but it has a 94.7% five-year survival rate when caught early. The standard way to spot a suspicious mole is the ABCDE rule, developed by the National Cancer Institute:
- Asymmetry: One half of the mole doesn’t match the other.
- Border: The edges are ragged, notched, or blurred rather than smooth. Pigment may spread into the surrounding skin.
- Color: The mole contains multiple shades of brown, black, or tan. You might also see areas of white, gray, red, pink, or blue.
- Diameter: Most melanomas are larger than 6 millimeters (about the size of a pencil eraser), though they can be smaller.
- Evolving: The mole has changed in any way over the past few weeks or months.
Not all melanomas follow these rules. Nodular melanoma, a fast-growing type, often appears as a firm, dome-shaped, raised bump that can resemble a blood blister. It develops quickly over weeks rather than months. Because it grows outward from the skin rather than spreading flat, it can be missed by the ABCDE criteria. Look for anything that is elevated, firm to the touch, and actively growing.
Signs of Basal Cell Carcinoma
Basal cell carcinoma is the most common skin cancer. It typically appears as a change in the skin that seems minor at first: a small bump, a pinkish patch, or a sore that heals and then reopens. On lighter skin, the classic sign is a shiny, translucent or pearly bump that looks skin-colored or slightly pink. Tiny blood vessels may be visible on or near the surface. On brown and Black skin, the bump often looks brown or glossy black with a raised, rolled border.
Another form shows up as a flat, white, waxy area that resembles a scar, with no clearly defined edge. This version is easy to overlook because it doesn’t look like a typical “growth.” The key feature across all forms of basal cell carcinoma is persistence. These spots bleed, scab over, and come back. A sore that won’t fully heal for several weeks is worth getting checked.
Signs of Squamous Cell Carcinoma
Squamous cell carcinoma often looks rougher and more textured than basal cell. Common signs include a firm bump or nodule on the skin, a flat sore topped with a scaly crust, or a wart-like raised growth. On lighter skin, these spots tend to be pink or red. On darker skin, they can be the same color as surrounding skin, or appear brown or black.
Pay attention to your lips, as a rough, scaly patch on the lip that evolves into an open sore can signal squamous cell carcinoma. This type can also develop inside the mouth or on the genitals. One distinctive pattern is a new raised area or sore appearing on top of an old scar or previous wound, which can happen years or even decades after the original injury.
Precancerous Spots to Watch
Actinic keratoses are rough, scaly patches caused by years of sun exposure. They aren’t cancer yet, but a small percentage develop into squamous cell carcinoma over time. They’re usually less than an inch across and feel like sandpaper when you run your finger over them. Colors range from pink to red to brown, and they tend to appear on sun-exposed areas like the face, scalp, ears, and backs of the hands. Some develop a hard, wart-like surface. If you notice rough patches that persist for weeks and don’t resolve on their own, they’re worth having evaluated.
How Skin Cancer Looks on Darker Skin
Skin cancer is less common in people with darker skin, but it’s often diagnosed later, which makes it more dangerous. Part of the problem is that the warning signs look different and tend to appear in places people don’t expect.
The most common melanoma in people with dark skin is acral lentiginous melanoma. It shows up on the palms of the hands, the soles of the feet, and under or around the fingernails and toenails. On these areas, look for dark patches, irregularly colored spots, or a dark vertical band running through a nail. Basal cell carcinoma can appear as a brown, glossy black, or tan bump with a rolled border. Melanoma may look like a dark or black bump with a waxy or shiny quality. These signs are easy to dismiss as bruises or normal pigmentation, so checking the palms, soles, and nails regularly matters.
Melanoma Under the Nails
Subungual melanoma appears as a dark, vertical streak running from the base of the nail to the tip. The streak is typically blackish-brown and may contain uneven shades of color. Over time, the line can widen, especially at the base of the nail, or multiply into additional streaks. One important warning sign, called Hutchinson’s sign, is when the dark pigment spreads beyond the nail onto the surrounding skin of the finger or toe.
In some cases there’s no visible dark streak at all. Instead, the nail may crack, split, lift away from the nail bed, or develop a small growth underneath. Any single nail that starts behaving differently from your others, especially without a clear injury to explain it, deserves attention.
Two Quick Detection Tricks
Beyond the ABCDE rule, there’s a useful concept called the “ugly duckling” sign. Most of your moles probably share a general family resemblance in terms of size, shape, and color. The ugly duckling is the one mole that looks nothing like the rest. It stands out. That outlier is worth monitoring closely or having a dermatologist examine, even if it doesn’t clearly meet ABCDE criteria.
The second trick is simply tracking change. A spot doesn’t need to look textbook-alarming to be concerning. Any mole, freckle, or patch that is new, growing, bleeding, crusting, or otherwise different from a few weeks ago is the kind of change that matters.
How to Do a Skin Self-Exam
A thorough self-check takes about 10 minutes and is easiest right after a shower. Stand in a well-lit room with a full-length mirror. Work through your body systematically:
- Front and back: Face the mirror, then turn around and look over your shoulders.
- Arms: Raise each arm and check the underarm, inner arm, and back of the upper arm (a commonly missed spot).
- Hands: Look at both sides, between the fingers, and under the nails.
- Legs: Check the front, back, and sides, including the inner thigh.
- Feet: Sit down and examine the soles, the spaces between your toes, and the toenails.
- Scalp and neck: Use a hand mirror and comb to part your hair and examine the scalp section by section. Check the back of the neck.
- Buttocks and genitals: Use a hand mirror for areas you can’t see directly.
Ask someone you trust to help with hard-to-see areas like your back and the back of your scalp. The goal isn’t to diagnose anything yourself. It’s to notice changes early so you can bring them to a dermatologist before they have a chance to progress.