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 and are often grouped together as “non-melanoma” skin cancers, accounting for millions of diagnoses each year in the United States. Melanoma is less common, with an estimated 112,000 new cases expected in 2026, but it’s significantly more dangerous because it spreads more readily to other parts of the body. A handful of rare skin cancers also exist, including Merkel cell carcinoma.
Basal Cell Carcinoma
Basal cell carcinoma (BCC) is the single most common type of skin cancer. It develops in basal cells, which sit in the deepest part of your outer skin layer and continuously produce new skin cells. BCC grows slowly, often taking decades to develop, and it rarely spreads to distant parts of the body. That said, it can destroy surrounding tissue if left untreated, particularly on the face or near the eyes, nose, or ears.
BCC most often appears on sun-exposed areas like the face and neck, though it can occasionally develop in places that rarely see sunlight, including the genitals. On lighter skin, it typically looks like a shiny, pearly, or slightly translucent bump, sometimes with tiny visible blood vessels running through it. On darker skin tones, BCC often appears as a brown or glossy black bump with a rolled border. Other forms include flat, scaly, flesh-colored patches or sores that bleed, scab over, and never fully heal. That failure to heal is one of the most reliable warning signs.
Squamous Cell Carcinoma
Squamous cell carcinoma (SCC) is the second most common skin cancer. It arises in the flat squamous cells that make up the outer surface of your skin. SCC is more aggressive than BCC. Most cases are caught early and treated successfully, but unlike basal cell carcinoma, SCC carries a meaningful risk of spreading to lymph nodes and other organs if it grows unchecked.
SCC can look quite different from one person to the next. Common presentations include a firm, raised nodule (pink, red, brown, or skin-colored), a flat sore topped with a scaly crust, or a rough, scaly patch on the lip that may turn into an open sore. It can also appear inside the mouth, on the genitals, or within old scars and chronic wounds. In fact, long-standing scars, burns, and sores that never fully healed are a recognized risk factor for SCC, alongside UV exposure from sunlight and tanning beds.
Actinic Keratosis: A Precancerous Warning
Actinic keratoses are rough, scaly patches caused by years of sun exposure. They aren’t cancer themselves, but they’re considered precancerous because they can progress into squamous cell carcinoma. Published estimates of that progression range widely, from less than 1% to 16% per year for any individual lesion, with an average hovering around 8% to 10%. The problem is that there’s no reliable way to predict which specific patch will become cancerous, which is why dermatologists generally recommend treating them.
Melanoma
Melanoma develops in the cells that give your skin its color. It’s the most dangerous common skin cancer because it tends to spread early if not caught. The good news is that when melanoma is found while still localized to the skin, the five-year survival rate is about 97.6%. Once it reaches nearby lymph nodes (regional spread), that drops to around 60%. If it has spread to distant organs, survival falls to roughly 16%. Early detection changes the outcome dramatically.
The ABCDE rule is the standard tool for spotting a suspicious mole:
- Asymmetry: one half of the mole doesn’t match the other.
- Border: edges are ragged, notched, or blurred, sometimes with pigment spreading into surrounding skin.
- Color: uneven shading with mixtures of black, brown, tan, white, gray, red, pink, or blue.
- Diameter: most melanomas are larger than about 6 millimeters (roughly the size of a pencil eraser), though they can be smaller.
- Evolving: the mole has changed in size, shape, or color over recent weeks or months.
Any mole that checks one or more of these boxes is worth having evaluated. Melanoma can appear anywhere on the body, including areas that rarely get sun exposure, like the soles of your feet or under a fingernail.
Merkel Cell Carcinoma and Other Rare Types
Several rare skin cancers exist beyond the big three. Merkel cell carcinoma is among the most notable. It forms in Merkel cells, which sit near nerve endings in the top layer of skin and help you sense touch. Merkel cell carcinoma is uncommon, but it’s aggressive. It grows quickly and tends to spread at an early stage.
A Merkel cell tumor typically appears on sun-exposed skin (the head, neck, arms, or legs) as a single, firm, dome-shaped lump that is painless and red or violet in color. Risk factors include extensive sun exposure, tanning bed use, being over 50, and having a weakened immune system from conditions like HIV or from medications taken after an organ transplant.
Other rare skin cancers include sebaceous gland carcinoma, which develops in the oil-producing glands of the skin, and Kaposi sarcoma, which forms in the lining of blood vessels and often appears as red or purple patches. Dermatofibrosarcoma protuberans is another rare type that grows in the deeper layers of skin. Together, these uncommon cancers make up a small fraction of all skin cancer diagnoses.
What All Skin Cancers Have in Common
Ultraviolet radiation is the dominant risk factor across nearly every type of skin cancer. UV light from the sun or tanning beds damages the DNA in skin cells. Normally, your cells can repair that damage, but over time, accumulated mutations can cause cells to grow out of control. This is why skin cancers cluster on sun-exposed areas and become more common with age.
Certain genetic conditions amplify this risk enormously. People with xeroderma pigmentosum, a rare inherited disorder where the body cannot properly repair UV-damaged DNA, are 10,000 times more likely to develop non-melanoma skin cancers and up to 2,000 times more likely to develop melanoma compared to the general population. While this condition is rare, it illustrates just how central DNA repair is to preventing skin cancer.
How Skin Cancer Is Diagnosed
Diagnosis starts with a visual exam, but confirmation always requires a biopsy, where a small sample of the suspicious area is removed and examined under a microscope. There are three main approaches, and which one your dermatologist uses depends on the size, depth, and location of the spot.
A shave biopsy scrapes a thin layer from the surface using a blade. It’s the least invasive option, typically doesn’t require stitches, and works well for shallow or surface-level growths. A punch biopsy uses a small round cutting tool to remove a deeper core of tissue, including layers beneath the surface. It may need a stitch or two. An excisional biopsy cuts out the entire suspicious area along with a border of healthy skin around it and generally requires stitches. This approach is often used when melanoma is suspected, because it gives the pathologist the full picture of how deep the growth extends.
Treatment Outlook by Type
Basal cell carcinoma has the best prognosis. Because it grows slowly and almost never spreads, it’s typically cured with surgical removal. Squamous cell carcinoma also has high cure rates when caught early, though larger or deeper tumors may require more extensive treatment. For high-risk SCC cases where cancer could return after surgery and radiation, newer immunotherapy options are now available to reduce recurrence.
Melanoma treatment depends almost entirely on the stage at diagnosis. Thin, early-stage melanomas are usually cured with surgery alone. More advanced melanoma may require immunotherapy or targeted therapy, treatments that either help your immune system recognize and attack cancer cells or block specific molecular pathways the cancer relies on to grow. These advances have significantly improved outcomes for advanced melanoma over the past decade.
Merkel cell carcinoma, given its tendency to spread early, is often treated with a combination of surgery, radiation, and immunotherapy. Despite its aggressiveness, earlier detection improves outcomes considerably, which is true across every type of skin cancer.