The signs of skin cancer depend on the type, but most share a common thread: a spot on your skin that looks different from the rest, changes over time, or won’t heal. The three most common types, basal cell carcinoma, squamous cell carcinoma, and melanoma, each have distinct visual clues worth knowing.
Signs of Basal Cell Carcinoma
Basal cell carcinoma is the most common form of skin cancer, and it often looks deceptively harmless. The classic sign is a slightly transparent, pearly bump on the skin. On lighter skin, the bump appears white or pink. Tiny blood vessels may be visible on or near the surface, giving it a slightly reddish tint. These bumps can bleed, scab over, and then seem to heal, only to bleed again.
Not all basal cell carcinomas look like bumps. Some appear as flat, scaly patches with or without a raised edge. Others look like waxy, scar-like areas with no clearly defined border, which makes them easy to overlook. On darker skin tones, they can show up as brown, black, or blue lesions with a slightly raised, translucent edge. The key pattern is a spot that keeps coming back, bleeds without a clear reason, or slowly changes shape over months.
Signs of Squamous Cell Carcinoma
Squamous cell carcinoma tends to look rougher and more aggressive than basal cell. It often shows up as a firm bump (called a nodule) that can 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.
One hallmark sign is a new sore or raised area that develops on an old scar or wound. On the lips, it may start as a rough, scaly patch that eventually becomes an open sore. Squamous cell carcinoma can also appear inside the mouth or on the genitals as a raised, wart-like growth. Any sore that persists for weeks without healing deserves attention.
Precancerous Patches to Watch
Before squamous cell carcinoma develops, many people first get rough, scaly spots on sun-exposed skin called actinic keratoses. These feel like sandpaper when you run your finger over them. They can be skin-colored, red, pink, brown, or gray, and they sometimes itch, sting, or bleed. Actinic keratoses appear on areas that have gotten the most sun over your lifetime: the face, ears, scalp, forearms, and backs of the hands. Most are treated before they progress, but without treatment, some do become squamous cell carcinoma.
Signs of Melanoma
Melanoma is less common than basal or squamous cell carcinoma but far more dangerous if not caught early. The widely used ABCDE rule, developed by the National Cancer Institute, describes its key features:
- Asymmetry: One half of the mole doesn’t match the other.
- Border irregularity: The edges are ragged, notched, or blurred rather than smooth. Pigment may spread into the surrounding skin.
- Color variation: Instead of one uniform shade, you see a mix of black, brown, tan, white, gray, red, pink, or blue within the same spot.
- Diameter: Most melanomas are larger than 6 millimeters across (roughly the size of a pencil eraser), though they can start smaller.
- Evolving: The mole has changed in size, shape, or color over recent weeks or months.
Of these five features, evolution is often the most useful in practice. A mole that has looked the same for years is far less concerning than one that’s recently shifted in any way.
The Ugly Duckling Sign
Beyond the ABCDE rule, there’s a simpler principle that catches melanomas the checklist sometimes misses. Most of your moles tend to look similar to one another. If one mole stands out from the rest, looking noticeably different in color, size, or shape, that “ugly duckling” deserves a closer look. This comparative approach is especially helpful when you have many moles and aren’t sure which ones are worth worrying about.
Melanoma in Unexpected Places
Not all melanomas appear as dark moles on sun-exposed skin. Some forms grow in places people rarely think to check.
Subungual melanoma develops under a fingernail or toenail. It typically appears as a dark brown or black vertical streak running from the bottom of the nail to the top, almost as if someone drew a line with a marker. The streak may start narrow (under 3 millimeters wide) and gradually widen, especially near the cuticle. Over time, the discoloration can spread to cover the entire nail. In some cases, instead of a dark streak, a small irregular growth develops and lifts the nail, or the nail cracks and deforms. This type of melanoma is more common on the thumb and big toe and occurs at higher rates in people with darker skin.
Acral melanoma appears on the palms, soles of the feet, or under the nails. Because people rarely examine these areas closely, it’s often caught at a later stage.
Melanoma Without Dark Pigment
A rare subtype called amelanotic melanoma lacks the dark coloring most people associate with skin cancer. These lesions are usually pink or light brown, making them easy to dismiss as a pimple, bug bite, or irritation. They don’t reliably follow the ABCDE criteria, which is why they’re harder to recognize. The most telling signs are a spot that doesn’t look like anything else on your skin, is growing quickly, or starts bleeding without an obvious cause.
Nodular Melanoma
Nodular melanoma is another aggressive subtype that can slip past the standard ABCDE check because it often grows as a dome-shaped bump rather than a flat, spreading mole. The “EFG rule” helps identify it: the lesion is elevated above the skin surface, firm to the touch (not soft or squishy), and growing noticeably over weeks to months. These tend to be uniform in color, sometimes dark, sometimes red or pink, which is precisely why they’re missed. Any firm, raised spot that’s actively growing should be evaluated promptly.
Benign Spots That Mimic Skin Cancer
Plenty of harmless skin growths can look alarming. Seborrheic keratoses are among the most common mimics. These are waxy, slightly raised, brown or tan spots that often have a “stuck on” appearance, as if you could peel them off the skin. They tend to develop after age 40 and can look dark enough to trigger melanoma concerns. Under close examination, seborrheic keratoses often have tiny cyst-like structures or pore-like openings within the lesion that melanomas lack. Still, if you can’t tell whether a dark spot is a harmless keratosis or something more serious, it’s worth getting it checked.
How to Check Your Own Skin
No major medical organization in the U.S. currently recommends routine skin cancer screening by a clinician for the general population, largely because there isn’t enough evidence yet to confirm that population-wide screening reduces harm. That puts more responsibility on you to know your own skin.
A monthly self-check is a reasonable habit. Use a full-length mirror and a hand mirror to examine your entire body, including your back, scalp, between your toes, and the soles of your feet. Check under your nails for dark streaks. The goal isn’t to diagnose anything yourself. It’s to notice change. When you know what your skin normally looks like, a new or evolving spot becomes obvious much earlier.
Pay particular attention to any spot that bleeds repeatedly, a sore that won’t heal within a few weeks, a mole that changes shape or color, or a new growth that looks different from everything else on your skin. These patterns cut across all skin cancer types and are the most reliable signals that something needs professional evaluation.