The three main types of skin cancer are basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and melanoma. Together they account for the vast majority of skin cancer diagnoses, though they differ significantly in how they look, how fast they grow, and how dangerous they become. BCC is by far the most common and least aggressive, SCC falls in the middle, and melanoma is the rarest of the three but the most likely to spread and become life-threatening.
Basal Cell Carcinoma: The Most Common Type
Basal cell carcinoma develops in the basal cells, which sit at the bottom of your outer layer of skin and continuously produce new skin cells. It’s the single most common form of cancer in humans, and it often takes decades of sun exposure to develop, which is why it shows up most frequently in older adults.
On lighter skin, BCC typically looks like a slightly transparent or pearly bump that’s skin-colored or pink. Tiny blood vessels may be visible on its surface. On brown and Black skin, it often appears as a brown or glossy black bump with a rolled border. BCC can also show up as a flat, scaly patch, a brown or blue lesion with dark spots, or a white, waxy, scarlike area without a clear edge. A hallmark sign is a sore that bleeds, scabs over, and then reopens.
The good news is that BCC almost never spreads to other parts of the body. It grows slowly and stays local, but left untreated it can grow quite large and damage surrounding tissue, including bone and cartilage. When caught early and treated surgically, cure rates are excellent. A specialized procedure called Mohs surgery, where thin layers of tissue are removed and examined one at a time, has a cure rate up to 99% for new BCC cases and up to 94% for cancers that have come back after previous treatment.
Squamous Cell Carcinoma: The Second Most Common
Squamous cell carcinoma starts in the flat squamous cells that make up the middle and outer layers of your skin. Like BCC, it’s primarily driven by cumulative UV exposure from sunlight or tanning beds, and it tends to appear on sun-exposed areas like the face, ears, hands, and arms. People who sunburn easily or who have weakened immune systems face higher risk.
SCC can look like a firm bump or nodule on the skin, a flat scaly patch that won’t go away, a new sore on an old scar, or a rough, wartlike growth. The color varies by skin tone: it can appear pink, red, brown, or black. On the lip, it may start as a rough, scaly patch that eventually opens into a sore. SCC can also develop inside the mouth or on the genitals.
SCC is more aggressive than BCC. It usually isn’t life-threatening, but if left untreated it can grow deep into the skin and occasionally spread to nearby lymph nodes or other organs. Mohs surgery cures 95% to 99% of new squamous cell carcinomas and about 90% of recurrent ones. The key is catching it before it has a chance to invade deeper tissue.
The Precancerous Stage: Actinic Keratosis
Many squamous cell carcinomas don’t appear out of nowhere. They grow from rough, scaly patches called actinic keratoses that develop on sun-damaged skin. Not every actinic keratosis becomes cancer. An individual lesion may regress on its own, stay unchanged, or progress to invasive SCC. One study tracking nearly 7,800 of these lesions found that about 0.6% progressed to SCC within one year and 2.57% within four years. That same study found that nearly 65% of primary squamous cell carcinomas arose from clinically diagnosed actinic keratoses, making them worth monitoring and treating early.
Melanoma: The Most Dangerous Type
Melanoma develops in melanocytes, the cells that produce the pigment giving your skin its color. It accounts for a small fraction of all skin cancers but causes the majority of skin cancer deaths. An estimated 112,000 new melanoma cases and 8,510 deaths are expected in the United States in 2026 alone.
What makes melanoma so dangerous is its ability to spread. When caught early and still confined to the skin, 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 like the lungs, liver, or brain, the five-year survival rate falls to 16.2%. Fortunately, about 83% of melanomas are diagnosed while still localized, which is why regular skin checks matter so much.
How to Spot Melanoma: The ABCDE Guide
Dermatologists use a simple memory tool to help people recognize potential melanomas on their skin:
- Asymmetry: One half of the mole or spot doesn’t match the other half.
- Border: The edges are irregular, ragged, or blurred rather than smooth.
- Color: The color isn’t uniform. You might see shades of brown, black, tan, red, white, or blue within the same spot.
- Diameter: The spot is larger than 6 millimeters across, roughly the size of a pencil eraser, though melanomas can be smaller.
- Evolving: The mole is changing in size, shape, or color over time.
If a suspicious spot is identified, doctors typically perform an excisional biopsy, removing the entire lesion with a small surgical blade so they can examine its full depth. This is different from the shave or punch biopsies more commonly used for suspected BCC or SCC, because knowing how deeply a melanoma has penetrated the skin is critical for determining its stage and treatment plan.
Melanoma on Darker Skin Tones
There’s a specific subtype called acral lentiginous melanoma that develops only on the palms of the hands, the soles of the feet, or under the nails. It appears as an unevenly pigmented dark spot on the palm or sole, or as a pigmented streak running from the cuticle to the tip of a fingernail or toenail.
This subtype is particularly important for people with darker skin. It doesn’t follow the same visual patterns as other melanomas, so the ABCDE guide is less useful for detecting it. People with more melanin are also less likely to think skin cancer can affect them, and they may not think to examine their nail beds, palms, or the bottoms of their feet. As a result, acral lentiginous melanoma is often not diagnosed until it bleeds or causes pain while walking, by which point it may be more advanced. Regardless of skin tone, regularly checking these often-overlooked areas is one of the most practical things you can do.
Why UV Radiation Causes All Three Types
Ultraviolet radiation is the common thread linking all three major skin cancers, but it damages skin cells through more than one mechanism. UVB rays, the kind that cause sunburn, directly damage the DNA in skin cells by fusing together neighboring building blocks in the genetic code. These fused pairs create errors when cells try to copy their DNA, leading to mutations that can drive cancer.
UVA rays, which penetrate deeper and make up the majority of UV exposure from sunlight, work differently. They generate unstable molecules called free radicals inside cells, which then attack DNA indirectly. Melanocytes are especially vulnerable to this kind of damage because melanin itself, the very pigment meant to protect skin, can act as a catalyst for producing these harmful molecules. Research has shown that melanocytes accumulate roughly twice as much of this oxidative DNA damage as the surrounding skin cells after UVA exposure. Even more unusually, melanocytes can continue generating DNA damage for hours after UV exposure ends, through a process sometimes called “dark” damage.
To make matters worse, melanocytes are naturally less efficient at repairing DNA damage than the keratinocytes that surround them. This combination of higher damage and weaker repair helps explain why melanoma, though less common, is so much more genetically unstable and prone to spreading than BCC or SCC.
Rarer Skin Cancers Beyond the Big Three
While BCC, SCC, and melanoma make up the overwhelming majority of skin cancers, a handful of rarer types exist. Merkel cell carcinoma is a fast-growing cancer that develops rapidly over weeks or months and can spread to lymph nodes, lungs, liver, or bones. It’s very rare, with only about 360 cases diagnosed per year in England, but its aggressive nature makes it far more dangerous per case than BCC or SCC. Sebaceous gland cancer starts in the oil-producing glands and can also spread to distant organs. Kaposi’s sarcoma, a type of soft tissue cancer that can affect the skin, and cutaneous lymphoma, a form of non-Hodgkin lymphoma that starts in the skin, round out the uncommon types. These rare cancers together represent a small fraction of diagnoses, which is why skin cancer discussions rightly focus on the three major types.