The three types of skin cancer are basal cell carcinoma, squamous cell carcinoma, and melanoma. Basal cell and squamous cell carcinomas are far more common and highly treatable, while melanoma is less common but significantly more dangerous because it can spread to other organs. Together, these three account for the vast majority of skin cancer diagnoses, though rarer forms do exist.
Basal Cell Carcinoma
Basal cell carcinoma is the most common type of skin cancer and the most common cancer of any kind. It starts in basal cells, which sit at the bottom of the epidermis, your skin’s outermost layer. These cells constantly divide to produce new skin cells that push older ones toward the surface. When UV radiation damages their DNA, they can begin growing out of control.
Basal cell carcinoma often looks like a slightly transparent or pearly bump on the skin. On lighter skin, it tends to appear skin-colored or pink, sometimes with tiny visible blood vessels on the surface. On darker skin tones, it often looks brown or glossy black with a rolled border. It can also show up as a flat, scaly patch or a sore that heals and then reopens. These growths typically appear on sun-exposed areas like the face, ears, neck, and scalp.
The good news is that basal cell carcinoma almost never spreads to distant parts of the body. It grows slowly and stays local, but if left untreated it can invade deeper tissue and cause significant damage to surrounding skin, muscle, and even bone. When caught early and removed surgically, cure rates are extremely high. A specialized technique called Mohs surgery, where a surgeon removes thin layers and checks each one under a microscope, has a cure rate up to 99% for new growths.
Squamous Cell Carcinoma
Squamous cell carcinoma is the second most common skin cancer. It begins in squamous cells, which make up the middle and outer layers of the skin. Like basal cell carcinoma, it’s driven primarily by cumulative UV exposure, and it most often shows up on sun-exposed areas: the scalp, backs of the hands, ears, and lips. Unlike basal cell carcinoma, it can also develop inside the mouth, on the soles of the feet, or on the genitals.
Squamous cell carcinoma typically appears as a firm bump or nodule that may be skin-colored, pink, red, brown, or black depending on skin tone. It can also look like a flat sore with a scaly crust, a rough patch on the lip that becomes an open sore, or a new raised area on an old scar. The key visual cue is often a persistent, scaly, or crusty spot that doesn’t heal.
This type is more aggressive than basal cell carcinoma. While most cases are caught early and cured with surgery, squamous cell carcinoma has a real capacity to spread to lymph nodes and other organs if left untreated, particularly in people with weakened immune systems. It also has a well-known precursor: actinic keratosis, those rough, sandpapery patches that develop on chronically sun-damaged skin. The risk of any single actinic keratosis progressing to invasive squamous cell carcinoma is low (estimates range from less than 1% to about 16% per year depending on the study), but people who have many of these spots carry a meaningful cumulative risk over time.
Melanoma
Melanoma is the least common of the three main types but by far the most dangerous. It starts in melanocytes, the cells that produce the pigment giving skin its color. Melanoma can develop in an existing mole or appear as a new dark spot on the skin. It can occur anywhere on the body, including areas that rarely see the sun.
Dermatologists use the ABCDE rule to spot melanoma early:
- Asymmetry: One half of the mole doesn’t match the other.
- Border: The edges are ragged, notched, or blurred rather than smooth.
- Color: The color is uneven, with shades of brown, black, tan, red, white, or blue within the same spot.
- Diameter: The spot is larger than about 6 millimeters (roughly the size of a pencil eraser), though melanomas can be smaller.
- Evolving: The mole has changed in size, shape, or color over recent weeks or months.
What makes melanoma so serious is its ability to metastasize, spreading through the lymphatic system or bloodstream to the lungs, liver, brain, or bones. When caught while still localized to the skin, the five-year survival rate is about 97.6%. Once it has spread to nearby lymph nodes, that drops to around 60%. If it reaches distant organs, survival falls to roughly 16%. About 83% of melanomas are diagnosed at the localized stage, which is why early detection matters so much.
How UV Radiation Causes All Three
Ultraviolet radiation is the single biggest risk factor shared across all three skin cancers, but different wavelengths do damage in different ways. UVB rays are the primary cause of sunburn and act directly on the DNA in your skin’s outer layer, creating specific types of DNA damage that can trigger mutations. UVA rays penetrate deeper into the skin and cause more indirect damage, generating reactive molecules that attack DNA from the inside. Both types contribute to skin cancer, which is why broad-spectrum sunscreen (blocking both UVA and UVB) matters.
Beyond UV exposure, other risk factors include fair skin, a history of blistering sunburns (especially in childhood), a weakened immune system, and a family history of skin cancer. For melanoma specifically, having a large number of moles or atypical moles raises your risk.
How They’re Treated
Treatment depends on the type, size, and location of the cancer, as well as how far it has progressed. For basal cell and squamous cell carcinomas caught early, surgical removal is the standard approach and is usually curative. Most procedures are outpatient, meaning you go home the same day. Recovery typically involves wound care for a few weeks and a small scar. For cancers on the face or in tricky locations, Mohs surgery offers the highest cure rates (up to 99% for new cancers, around 95% for recurrences) while removing as little healthy tissue as possible.
Melanoma treatment depends heavily on how deep the cancer has grown into the skin. Thin, early-stage melanomas are surgically removed with a margin of healthy skin around them, and that’s often all that’s needed. Thicker or more advanced melanomas may require removal of nearby lymph nodes, followed by immunotherapy or targeted drug therapy to reduce the chance of recurrence. Treatment for advanced melanoma has improved dramatically in recent years, but outcomes are still far better when it’s caught early.
Other Skin Cancers Beyond the Big Three
While basal cell, squamous cell, and melanoma make up the vast majority of cases, rarer skin cancers do exist. Merkel cell carcinoma, for example, affects about 3,000 Americans per year. It tends to strike people over 70, is more common in men and in people with weakened immune systems, and is more aggressive than the common non-melanoma cancers. Other rare types include dermatofibrosarcoma and sebaceous carcinoma. These are uncommon enough that most people will never encounter them, but any new, changing, or non-healing spot on the skin is worth getting checked.
What to Watch on Your Own Skin
No major medical organization in the U.S. currently recommends routine skin cancer screening for people without symptoms or risk factors. The U.S. Preventive Services Task Force has said the evidence is insufficient to assess whether whole-body skin exams by a clinician help the average person. That puts much of the responsibility on you to know your own skin.
Monthly self-checks are the simplest tool. Stand in front of a full-length mirror and use a hand mirror for your back, scalp, and other hard-to-see areas. You’re looking for anything new, anything that’s changed, and anything that won’t heal. A pimple that doesn’t go away after a month, a mole that shifts in color or shape, a shiny bump that bleeds and scabs over repeatedly. These are the signals worth acting on.