Skin cancer shows up in several forms, and its symptoms depend on the type. The most common warning sign across all types is a change in your skin: a new growth, a sore that won’t heal, or a mole that starts looking different. Knowing what each type looks like helps you spot problems early, when treatment is simplest.
Melanoma and the ABCDE Rule
Melanoma is the most dangerous form of skin cancer, but it’s also one of the easiest to catch early if you know what to look for. Dermatologists use a five-letter framework to describe the warning signs:
- 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 the surrounding skin.
- Color: Instead of one uniform shade, you see a mix of brown, tan, black, or even patches of white, gray, red, pink, or blue.
- Diameter: Most melanomas are larger than 6 millimeters across (roughly the size of a pencil eraser), though they can be smaller.
- Evolving: The mole has changed in size, shape, or color over the past few weeks or months.
A mole doesn’t need to check every box to be suspicious. Any single change, especially rapid evolution, is worth getting examined.
The “Ugly Duckling” Sign
If you have many moles or freckles, there’s a simpler way to scan your skin. Look for the one spot that doesn’t match the rest. Maybe it’s scabbed over, more raised, or a different color than your other moles. Dermatologists call this the “ugly duckling” sign: a single mole or freckle that stands out from the pattern on your body. It can be an early indicator of melanoma even when the ABCDE features aren’t obvious yet.
Basal Cell Carcinoma Symptoms
Basal cell carcinoma is the most common skin cancer. It grows slowly and rarely spreads to other parts of the body, but it can damage surrounding tissue if left alone. Its appearance varies quite a bit depending on skin tone.
On lighter skin, basal cell carcinoma often looks like a slightly transparent or pearly bump that’s skin-colored or pink. Tiny blood vessels may be visible on or near the surface. On brown and Black skin, it tends to appear as a brown or glossy black bump with a rolled border. In both cases, the bump may bleed, scab over, and then reopen.
Not all basal cell carcinomas look like bumps, though. Some show up as a flat, scaly patch with a raised edge. Others resemble a white, waxy, scar-like area without a clearly defined border. A brown, black, or blue lesion with dark spots and a slightly raised, translucent border is another presentation. The key pattern is a skin change that persists, slowly grows, or repeatedly scabs without fully healing.
Squamous Cell Carcinoma Symptoms
Squamous cell carcinoma is the second most common type. It’s more aggressive than basal cell carcinoma and can spread if untreated, so catching it early matters. Common signs include:
- A firm bump (nodule) that may be pink, red, brown, black, or the same color as your skin
- A flat sore with a scaly crust
- A new sore or raised area developing on an old scar
- A rough, scaly patch on the lip that may turn into an open sore
- A sore or rough patch inside the mouth
- A raised, wartlike sore on or near the genitals or anus
A general rule of thumb: any sore or scab that doesn’t heal within about two months, or a flat scaly patch that won’t go away, deserves a professional look.
Itching, Pain, and Other Sensations
Skin cancer isn’t always painless. Some people notice persistent itching around a growth, while others feel tenderness or pain near a changing lesion. These sensations don’t happen in every case, but they’re worth paying attention to, especially if they accompany a visible skin change. Spontaneous bleeding from a mole or bump, without any injury, is another red flag across all skin cancer types.
Skin Cancer in Hidden Locations
Most people check sun-exposed areas like their face, arms, and chest. But skin cancer can develop in places you’d never think to look. Acral lentiginous melanoma forms on the palms, soles of the feet, and under the nails. Unlike other melanomas, it isn’t linked to sun exposure, and it’s the most common type of melanoma in people with darker skin tones.
Under a nail, this cancer typically appears as a dark brown or black vertical streak running from the base of the nail to the tip. It may look like someone drew a line with a marker. The streak can start narrow and gradually widen to cover the entire nail, sometimes extending into the cuticle. It most commonly affects the big toe, thumb, or index finger. A new dark streak under a nail that wasn’t caused by an injury should be evaluated.
Pre-Cancerous Patches to Watch
Not every concerning spot is cancer yet. Actinic keratoses are rough, scaly patches caused by years of sun exposure. They typically show up on the head, neck, arms, and hands. On the head and neck they tend to lie flat, while on the arms and hands they feel more like small bumps. The color ranges from tan and pink to red, or sometimes matches the surrounding skin. The surface often feels dry, rough, or crusty.
These patches matter because a small percentage of them progress into squamous cell carcinoma over time. They’re essentially a warning that your skin has accumulated significant sun damage. Treating them early removes that risk entirely.
Rare Types Worth Knowing
Merkel cell carcinoma is uncommon but aggressive. It appears as a firm bump on the skin that grows quickly, often over just a few weeks. The bump is usually painless and can look pink, purple, red-brown, or skin-colored. Its sides may not match each other, similar to melanoma’s asymmetry. Because it grows fast and can spread early, any rapidly enlarging bump on the skin warrants prompt attention.
How Most Skin Cancers Get Found
The majority of melanomas are discovered either by patients noticing something on their own skin or by a clinician spotting it incidentally during an exam for something else. There’s no universally recommended screening schedule in the U.S. for the general population. That puts a lot of the detection responsibility on you.
Get familiar with your own skin. Know where your moles are and what they look like. Check your entire body periodically, including your scalp, the spaces between your toes, your nail beds, and your back (use a mirror or ask someone to help). The goal isn’t to diagnose yourself. It’s to notice when something changes, so you can get it checked before it becomes a bigger problem.