There are three main types of skin cancer: basal cell carcinoma, squamous cell carcinoma, and melanoma. Basal cell and squamous cell carcinomas are by far the most common, accounting for roughly 6.1 million treated cases per year in the United States alone. Melanoma is less common but significantly more dangerous because of its tendency to spread. A handful of rare skin cancers also exist, including Merkel cell carcinoma and dermatofibrosarcoma protuberans.
Basal Cell Carcinoma
Basal cell carcinoma is the most frequently diagnosed skin cancer. It starts in the basal cells, which sit at the bottom of the outer layer of skin and continuously produce new skin cells. It almost always develops on sun-exposed areas, particularly the face and neck, though it can occasionally appear in areas that rarely see sunlight.
What it looks like varies. The most recognizable form is a shiny, translucent bump that looks pearly white or pink on lighter skin and brown or glossy black on darker skin. Tiny blood vessels may be visible on the surface. Other forms include a brown or blue lesion with a slightly raised border, a flat scaly patch, or a white waxy area that resembles a scar without a clear edge. A hallmark sign is a sore that bleeds, scabs over, and then reopens without fully healing.
Basal cell carcinoma grows slowly and very rarely spreads to distant parts of the body. That doesn’t make it harmless. Left untreated, it can invade and destroy surrounding tissue, including cartilage and bone, especially around the nose and eyes. Because it tends to stay local, treatment is highly effective when caught early.
Squamous Cell Carcinoma
Squamous cell carcinoma is the second most common skin cancer. It begins in the flat squamous cells that make up most of the skin’s outer surface. Like basal cell carcinoma, it favors sun-exposed skin, but it also shows up on the lips, inside the mouth, and on the genitals.
It typically appears as a firm bump (sometimes the same color as surrounding skin, sometimes red, pink, brown, or black), a flat sore with a scaly crust, or a rough patch on the lip that may break open. A new sore or raised area on an old scar is another warning sign.
Squamous cell carcinoma carries a higher risk of spreading than basal cell carcinoma, though this is still uncommon overall. The risk increases when the tumor grows large or deep, involves mucous membranes like the lips, or develops in someone with a weakened immune system. When it does spread, it typically reaches nearby lymph nodes first.
Actinic Keratosis: A Precancerous Stage
Many squamous cell carcinomas start as actinic keratoses, rough scaly patches caused by years of sun exposure. About 10% of these precancerous spots progress to squamous cell carcinoma, and that progression takes roughly two years on average. Treating actinic keratoses early, usually with freezing or topical creams, can prevent them from becoming cancerous.
Melanoma
Melanoma develops in melanocytes, the cells that produce the pigment giving skin its color. It accounts for a small fraction of all skin cancers but causes the majority of skin cancer deaths. The reason is biological: melanoma cells are far more likely to break away from the original tumor, enter the bloodstream or lymphatic system, and establish new tumors in distant organs like the lungs, liver, or brain.
Melanoma can develop anywhere on the body, including areas that never see the sun. It often appears as a new, unusual-looking mole or as changes in an existing mole. The ABCDE rule is the standard tool for spotting warning signs:
- Asymmetry: one half of the mole doesn’t match the other
- Border: edges are ragged, notched, or blurred, with pigment possibly spreading into surrounding skin
- Color: multiple shades of brown, black, or tan, sometimes with areas of white, gray, red, pink, or blue
- Diameter: larger than 6 millimeters (about the size of a pencil eraser), though melanomas can be smaller
- Evolving: the mole has changed in size, shape, or color over weeks or months
Survival depends heavily on when melanoma is caught. When it’s still confined to the original site, the five-year survival rate is 97.6%. Once it spreads to nearby lymph nodes, that drops to 60.3%. If it reaches distant organs, it falls to 16.2%. This dramatic difference is why early detection matters more with melanoma than with almost any other cancer.
Rare Skin Cancers
Several uncommon skin cancers are worth knowing about, even though you’re unlikely to encounter them.
Merkel cell carcinoma forms in the touch-receptor cells near nerve endings in the top layer of skin. It’s very rare but aggressive, tending to grow quickly and spread at an early stage. It’s actually the second leading cause of skin cancer death after melanoma. It usually appears on sun-exposed areas as a single firm, dome-shaped lump that’s red or violet and painless. People over 50, men, those with fair skin, and anyone with a weakened immune system face the highest risk.
Dermatofibrosarcoma protuberans (DFSP) is a rare cancer that starts in the deep layers of the skin. It grows slowly and rarely spreads to distant sites, but it has a notable tendency to come back after surgical removal, which often means repeat procedures are needed to fully clear it.
How Skin Cancers Are Treated
Treatment depends on the type, size, location, and how deep the cancer has grown. For basal cell and squamous cell carcinomas caught early, treatment is often straightforward: a minor procedure done under local anesthesia, sometimes in a dermatologist’s office rather than an operating room.
One specialized technique, called Mohs surgery, removes the visible cancer plus a thin layer of surrounding tissue, then examines that tissue under a microscope immediately. If cancer cells remain at the edges, another thin layer is removed and checked. This process repeats until no cancer is found. The advantage is precision: it removes all the cancer while preserving as much healthy skin as possible, which is especially valuable near the eyes, nose, ears, and mouth. Mohs surgery is used for basal cell carcinoma, squamous cell carcinoma, melanoma, and some rarer skin cancers, particularly when tumors are large, have unclear borders, or have returned after previous treatment.
Melanoma treatment is more involved. Thin, early-stage melanomas may only need surgical removal with a margin of healthy tissue around them. More advanced melanomas may require removal of nearby lymph nodes, immunotherapy to help the body’s own immune system fight remaining cancer cells, or targeted drug therapies. The treatment path depends largely on how deep the melanoma has grown and whether it has spread.
What Sets Each Type Apart
The practical distinction between skin cancer types comes down to two things: how they look and how they behave. Basal cell carcinoma is the slowest and least likely to spread, but it can cause serious local damage if ignored. Squamous cell carcinoma grows faster and has a real, if small, chance of spreading. Melanoma is the most aggressive of the common types and can become life-threatening quickly if not caught early. The rare types, especially Merkel cell carcinoma, can be even more aggressive than melanoma despite being far less well known.
All skin cancers share one important feature: they are more treatable when found early. Regular self-checks of your skin, paying attention to new growths or changes in existing spots, remain the simplest and most effective way to catch any type before it becomes a serious problem.