There are three main types of skin cancer: basal cell carcinoma, squamous cell carcinoma, and melanoma. Basal cell carcinoma is the most common by far, followed by squamous cell carcinoma, with melanoma being less common but significantly more dangerous. Beyond these three, several rare skin cancers exist, including Merkel cell carcinoma, sebaceous gland carcinoma, and Kaposi sarcoma. An estimated 112,000 new cases of melanoma alone are expected in the United States in 2026, and non-melanoma skin cancers number in the millions annually.
Basal Cell Carcinoma
Basal cell carcinoma (BCC) is the most frequently diagnosed skin cancer worldwide. It develops in the basal cells, which sit at the bottom of the outer layer of skin and produce new skin cells as old ones die off. BCC grows slowly and rarely spreads to other parts of the body, but it can cause significant local damage if left untreated, growing into nearby bone or tissue.
BCC can look quite different depending on the person and the location. Common appearances include:
- A shiny, translucent bump that looks pearly white or pink on lighter skin, or brown to glossy black on darker skin. Tiny blood vessels may be visible on the surface, and it may bleed and scab over repeatedly.
- A brown, black, or blue lesion with dark spots and a slightly raised, translucent border.
- A flat, scaly patch with or without a raised edge that can grow quite large over time.
- A white, waxy, scarlike lesion without a clearly defined border.
Because BCC tends to develop on sun-exposed areas like the face, neck, and arms, many people first notice it as a sore that heals and then reopens, or a bump that simply won’t go away. That “sore that won’t heal” pattern is one of the most reliable early warning signs.
Squamous Cell Carcinoma
Squamous cell carcinoma (SCC) is the second most common skin cancer. It develops in the flat cells that make up the outer surface of the skin. Unlike BCC, SCC carries a meaningful risk of spreading to lymph nodes and other organs if it isn’t caught and treated, though most cases are curable when detected early.
SCC most often appears on sun-exposed skin: the scalp, backs of the hands, ears, and lips. But it can develop anywhere on the body, including inside the mouth, on the soles of the feet, and on the genitals. In people with darker skin tones, squamous cell carcinomas are actually more likely to appear on skin that doesn’t get much sun, such as the genitals.
Visually, SCC can show up as a firm nodule that may be skin-colored, pink, red, brown, or black. It can also appear as a flat sore with a scaly crust, a rough or scaly patch on the lip that evolves into an open sore, or a raised, wartlike growth. A new sore developing on an old scar is another pattern worth watching for.
Actinic Keratosis: A Precancerous Warning
Actinic keratoses are rough, scaly patches caused by years of sun exposure. They aren’t skin cancer, but they are considered precancerous because a small percentage can progress to squamous cell carcinoma. The individual risk per lesion is low: the estimated annual progression rate is 0% to 0.075% for a single spot. But people who have many of these patches face higher cumulative risk. Among older patients with multiple lesions, the annual rate of progression to invasive SCC reaches about 0.6%, climbing to roughly 2.5% within four years of diagnosis. Dermatologists often treat actinic keratoses proactively for this reason.
Melanoma
Melanoma develops in melanocytes, the cells that give skin its color. It accounts for a small fraction of all skin cancer diagnoses but causes the majority of skin cancer deaths. When caught early, melanoma is highly treatable. The five-year survival rate for localized melanoma (stages I and II) is 97.6%. Once it spreads to nearby lymph nodes, that rate drops to 60.3%, and for melanoma that has reached distant organs, it falls to 16.2%. About 83% of melanomas are diagnosed while still localized, which is encouraging but also underscores how important early detection is.
The ABCDE rule, developed by the National Cancer Institute, gives you a practical framework for evaluating moles and spots:
- Asymmetry: One half of the mole doesn’t match the other.
- Border: The edges are ragged, notched, or blurred rather than smooth. Pigment may spread into the surrounding skin.
- Color: The color is uneven, with shades of black, brown, tan, white, gray, red, pink, or blue mixed together.
- Diameter: The spot is larger than about 6 millimeters (roughly the size of a pencil eraser), though melanomas can sometimes be smaller.
- Evolving: The mole has changed in size, shape, or color over recent weeks or months.
Not every melanoma follows all five criteria, and not every irregular mole is melanoma. But any mole that checks two or more of these boxes, or one that is clearly evolving, warrants a professional evaluation.
Rare Types of Skin Cancer
Several uncommon skin cancers exist beyond the big three. They are far less likely, but some are aggressive and worth knowing about.
Merkel Cell Carcinoma
Merkel cell carcinoma is a fast-growing cancer that typically appears as a painless, firm nodule on sun-exposed skin, often on the face, head, or neck. It most commonly affects people over 50, particularly those with lighter skin that sunburns easily. A weakened immune system significantly raises risk, whether from HIV, chronic leukemia, or medications that suppress immune function after an organ transplant. People with a history of other skin cancers, including BCC or SCC, also face higher odds.
Sebaceous Gland Carcinoma
This cancer arises in the oil-producing glands of the skin and most frequently appears on the eyelid. It typically shows up as a firm nodule or as diffuse thickening of the eyelid, sometimes with eyelash loss. The American Academy of Ophthalmology calls it “the great masquerader” because it mimics benign conditions so effectively. It is commonly mistaken for a recurring stye or chronic eyelid inflammation, leading to an average delay of one to three years before correct diagnosis. Even under a microscope, it gets misidentified as basal or squamous cell carcinoma in 40 to 75 percent of cases when reviewed by pathologists unfamiliar with it.
Kaposi Sarcoma
Kaposi sarcoma is caused by a specific herpesvirus. Most people infected with this virus never develop cancer, but certain groups are vulnerable. The HIV-associated form (epidemic Kaposi sarcoma) is the most well-known, but transplant recipients on immune-suppressing medications, older men of Mediterranean or Eastern European Jewish heritage, and young men in parts of Africa can also develop it. Kaposi sarcoma usually begins as red, purple, or brown skin lesions on the legs and feet, most often around the ankles or soles.
How Skin Cancer Is Diagnosed
A dermatologist will first examine a suspicious spot visually, often using a handheld magnifying device called a dermatoscope. If anything looks concerning, the next step is a biopsy, which means removing a small sample of tissue and sending it to a lab. There are three main biopsy approaches, and the one your dermatologist chooses depends on the size, depth, and location of the spot.
A shave biopsy scrapes off the top layers of skin with a blade and typically doesn’t require stitches. It works well for shallow, surface-level growths. A punch biopsy uses a small, round cutting tool to remove a deeper core of tissue, including layers below the surface. Depending on the size, it may need a stitch or two. An excisional biopsy removes an entire lump or suspicious area along with a border of healthy skin around it, and almost always requires stitches. This approach is often used when melanoma is suspected, since the lab needs to evaluate the full depth and margins of the growth.
The biopsy itself is done under local anesthesia and takes only a few minutes. Results typically come back within one to two weeks and will confirm whether cancer is present, what type it is, and how deeply it has grown, all of which guide the treatment plan.