Cancers can look surprisingly different depending on where they appear, but most share a few visual red flags: irregular shape, uneven color, changes over time, and borders that look ragged or blurred. Some cancers are visible on the skin’s surface, while others show up as subtle changes in texture, color, or shape on areas you might not think to check, like your nails, the soles of your feet, or inside your mouth. Here’s what to look for across the most common types.
Skin Cancer: The Three Main Types
Skin cancers are the most visually identifiable cancers, and each of the three major types has a distinct appearance.
Basal cell carcinoma is the most common. On lighter skin, it typically shows up as a pale, pink, or red bump that looks shiny or pearly. It may have tiny visible blood vessels running through or around it, and it can bleed after even minor contact. On darker skin tones, basal cell carcinoma often appears as a glossy brown, black, or tan bump with a rolled, raised border.
Squamous cell carcinoma tends to look flatter. It often appears as a reddish or brownish patch with a rough, scaly, or crusted surface. The area may become swollen, start oozing, or bleed. On darker skin, it can show up as a firm bump, a flat sore, or a scaly patch that may match your natural skin tone or appear pink, red, brown, or black. It sometimes develops on old scars or areas of chronic skin damage.
Melanoma is the most dangerous skin cancer, and it has the most distinctive warning signs. Dermatologists use the ABCDE rule to describe what to watch for:
- Asymmetry: One half of the mole or spot doesn’t match the other.
- Border irregularity: The edges are ragged, notched, or blurred, and pigment may spread into surrounding skin.
- Color variation: The spot contains multiple shades of brown, black, or tan, possibly with areas of white, red, pink, gray, or blue.
- Diameter: Most melanomas are larger than 6 millimeters (about the size of a pencil eraser), though they can be smaller.
- Evolving: The spot has changed in size, shape, or color over recent weeks or months.
A normal mole, by contrast, is usually symmetrical, has smooth and even borders, is one uniform color, and stays the same over time. If a mole suddenly breaks any of those rules, that’s worth getting checked.
What Skin Cancer Looks Like on Dark Skin
Skin cancer in people with darker skin tones often appears in different locations and can look different from the textbook images most people have seen. The most common form of melanoma in people with dark skin is acral lentiginous melanoma, which develops on the palms, soles of the feet, fingers, toes, and under the nails. It can look like a dark patch on your palm or the bottom of your foot, or a dark band running lengthwise under a fingernail or toenail.
Melanoma on dark skin may also appear as a dark or black bump that looks waxy or shiny. Because these cancers often occur in spots that aren’t sun-exposed, they’re easy to overlook. Checking your palms, the soles of your feet, and your nail beds regularly is especially important.
Cancer Under Your Nails
Subungual melanoma, a cancer that forms beneath the nail, typically starts as a dark vertical streak running from the base of the nail to the tip. The streak is usually blackish-brown with uneven coloring, and it may start narrow (under 3 millimeters wide) before gradually widening, especially at the base of the nail. Over time, the line can become irregular in shape and multiply into additional streaks.
One key warning sign is called Hutchinson’s sign: the dark pigment spreads beyond the nail itself and discolors the surrounding skin at the cuticle or nail fold. If you notice a new dark line under a nail that’s widening or changing, or if the pigment is bleeding into the skin around the nail, that warrants a closer look from a dermatologist.
Breast Cancer: Changes You Can See
Most breast cancers aren’t visible from the outside, but inflammatory breast cancer is the exception. It causes changes you can see and feel on the skin of the breast. The hallmark sign is skin that looks dimpled and pitted, similar to the surface of an orange peel. This happens because cancer cells block the lymph vessels in the skin, causing swelling and texture changes.
Other visible signs include redness or color changes across part or all of the breast, a nipple that suddenly flattens or turns inward, and skin that feels warm or thickened. Inflammatory breast cancer can progress quickly and doesn’t always involve a distinct lump, so these surface-level changes are often the first clue.
Oral Cancer: White and Red Patches
Inside the mouth, cancer and precancer show up as persistent patches that don’t heal. There are two main types to know about. White patches (called leukoplakia) are flat, persistent white areas on the gums, tongue, floor of the mouth, or inner cheeks. About 25% of these white patches turn out to be cancerous or precancerous. Some patches are a mix of red and white.
Red patches (erythroplakia) are more alarming. These are raised, persistent red areas that bleed if scraped. Roughly 90% of red patches in the mouth are cancerous or precancerous. Any sore, patch, or discolored area in your mouth that hasn’t healed within two to three weeks is worth having evaluated, particularly if it bleeds easily or feels different from the tissue around it.
A White Glow in a Child’s Eye
In children, one of the most recognizable cancer signs is a white, gray, silvery, or yellow glow in the pupil of the eye, instead of the normal red-eye effect you see in flash photographs. This is called leukocoria, sometimes described as “cat’s eye pupil,” and it can be a sign of retinoblastoma, a childhood eye cancer.
Parents sometimes first notice it in photographs taken with a flash, where one eye glows red normally and the other appears white. A surface reflection off the eye can occasionally mimic this, but a true leukocoria fills most or all of the pupil and appears consistently across multiple photos. If you see this pattern repeatedly in pictures of your child, especially when the white reflection fills the entire pupil, bring it up with their pediatrician promptly.
Swollen Lymph Nodes
Lymph nodes swell for many reasons, and most of the time the cause is a routine infection. But cancerous lymph nodes do have characteristics that set them apart, particularly on imaging. Normal lymph nodes are bean-shaped and have a bright fatty center visible on ultrasound. Cancerous nodes tend to become round, lose that fatty center, and may show abnormal blood flow patterns around their edges rather than through the middle.
From the outside, a swollen lymph node that’s hard, painless, fixed in place (doesn’t move when you press it), or continues growing over several weeks is more concerning than one that’s soft, tender, and appeared alongside a cold or infection. Cancerous nodes can appear in the neck, armpits, or groin, and they typically don’t shrink on their own the way infection-related swelling does.
General Patterns Across Cancer Types
While every cancer type has its own specific appearance, a few visual themes come up repeatedly. Irregularity is one: uneven borders, asymmetric shapes, and mixed colors are more suspicious than smooth, uniform, single-colored spots. Change over time is another. A mole that’s looked the same for 20 years is far less concerning than one that shifted shape last month. Persistence matters too. Sores that don’t heal, patches that don’t fade, and lumps that don’t shrink after a few weeks all deserve attention.
Color can be a clue across many cancer types. Multiple colors within a single spot, unexpected pigmentation (like dark streaks under nails), and color that spreads beyond the original boundary of a lesion are all warning signs. Texture changes also matter: skin that becomes pitted, scaly, pearly, or shiny in a localized area may be signaling something beneath the surface.