Skin cancer is far and away the most common cancer in the United States, affecting an estimated 1 in 5 Americans by the age of 70. (1)

Skin cancer is the rampant growth of abnormal skin cells. The cause is usually excessive exposure to ultraviolet (UV) radiation, either from sunlight or indoor tanning devices.

UV radiation can damage the DNA of skin cells, resulting in mutations (genetic defects). These mutations instruct the abnormal skin cells to multiply at a rapid pace, forming malignant tumors. (2)

Basal cell carcinoma and squamous cell carcinoma, the most common types of skin cancer, tend to develop on parts of the body that get a lot of sun exposure, such as the face, ears, neck, lips, and the backs of the hands.

To understand skin cancer, you need a basic understanding of skin cells. There are three main types in the epidermis (the top layer of skin), all of which have the potential to become malignant.

• Squamous Cells These flat cells are in the outer part of the epidermis. The body continually sloughs off old squamous cells as it makes new ones.
• Basal Cells These cells start in the base of the epidermis and base of the hair follicle. They mature and become larger as they grow into the upper level of the skin (toward the surface) to become new squamous cells.
• Melanocytes These cells produce melanin, a pigment that gives skin its brown or tan color. They act as a natural sunscreen, helping protect layers of skin below the epidermis from UV damage.

Most Common Skin Cancers

There are three main categories of skin cancer as well as a number of rare kinds.

• Basal Cell Carcinoma This cancer accounts for about 80 percent of all cases of skin cancer. It is almost always completely curable, rarely spreading to other parts of the body. Left untreated, however, it can destroy skin, deep tissue, and bone, becoming disfiguring or causing functional problems.
• Squamous Cell Carcinoma Accounting for about 20 percent of all skin cancers, this carcinoma is also highly treatable. However, it is more likely than basal cell carcinoma to spread. Although metastatic squamous cell cancer is uncommon, it can be life-threatening.
• Melanoma This form of cancer, which develops in the melanocytes, makes up only about 1 percent of all skin cancers. As with basal and squamous cell carcinomas, it is very curable if diagnosed early. If it is not treated quickly, however, it is more likely than these other skin cancers to metastasize and can prove fatal. (4)

Rare Types of Skin Cancer

The following diseases make up less than 1 percent of all skin cancers.

• Merkel Cell Carcinoma This cancer develops in cells found at the base of the epidermis, close to nerve endings. It is very aggressive, with a high risk of metastasizing. (5)
• Kaposi Sarcoma (KS) A cancer of the cells that line lymph or blood vessels, KS appears as lesions on the skin, inside the mouth, or elsewhere in the body. In the United States, the most common type of KS develops in people who have the HIV virus. (6)
• Cutaneous (Skin) Lymphoma This cancer starts in white blood cells, called lymphocytes, in the skin. (7)
• Skin Adnexal Tumors These cancers start in hair follicles or skin glands.
• Various Types of Sarcomas

How Prevalent Is Skin Cancer?

It’s estimated that in the United States, more than 3.3 million people are diagnosed and treated each year for 5.4 million basal cell and squamous cell carcinomas.

In a troubling trend, the incidence of all types of cancers has been going up for years.

Researchers have found that the number of people receiving a diagnosis of basal cell carcinoma more than doubled between the time spans between 1976–1984 and 2000–2010.

The incidence of squamous cell carcinoma shot up 263 percent over the same periods.

Women had the greatest jump for both basal cell and squamous cell carcinomas, with people age 40 and below also showing a disproportionate increase. (1)

Melanoma rates are also rising at an alarming pace. From 2008 to 2018, the number of new cases diagnosed annually increased by 53 percent.

The popularity of indoor tanning beds may help explain these numbers. Researchers believe that indoor tanning devices may be responsible for more than 419,000 cases of skin cancer in the United States each year: 245,000 basal cell carcinomas, 168,000 squamous cell carcinomas, and 6,200 melanomas. (8)

So You’ve Had Skin Cancer. Now What?

Melanoma survivors may well be expected to be alert for a recurrence, but anyone who’s had any type of skin cancer should remain extra vigilant.

This entails being scrupulous about scheduling follow-up visits to the dermatologist (or oncologist), conducting frequent skin self-exams, and limiting UV exposure.

If not removed completely, basal cell carcinoma can grow back on the same place on the skin. People who have had basal cell cancer are at higher risk of developing it again in other areas of the skin, too. (4)

People with squamous cell carcinoma are also at increased risk for recurrence, especially in the same skin area or nearby. Growths on the nose, ears, and lips pose the highest risks. (9)

Studies also suggest that people with basal or squamous cell cancers are at increased risk of developing another type of cancer, particularly melanoma. For women, this risk also includes breast and lung cancer. (10)

If you want to lower your risk of skin cancer, the smartest thing you can do is to minimize your exposure to ultraviolet (UV) rays. Experts blame UV rays for 90 percent of basal cell and squamous cell carcinomas and (according to one study) 86 percent of melanomas. Both the UV rays produced by sunlight and those created by indoor tanning devices damage the DNA of skin cells, creating genetic mutations that prompt those cells to multiply wildly and form tumors. Certain physical characteristics can make you especially vulnerable to the harmful effects of UV rays, such as fair skin; blue, green, or gray eyes; and blond, red, or light-brown hair.

Learn More About Causes and Risk Factors

There are three main categories of skin cancer, each affecting a different type of skin cell. Basal cell cancer is the kind you’re most likely to get, accounting for around 80 percent of all skin carcinomas. This cancer grows slowly and is extremely unlikely to spread. If left untreated, however, it can become disfiguring or lead to functional problems. Squamous cell cancer accounts for roughly 20 percent of all skin cancers. It’s more likely to spread than basal cell cancer, but the overall risk remains very low. Melanoma is the least common skin cancer, accounting for less than 1 percent of all skin cancers, but the most likely to spread and to become life-threatening.

Learn More About the Types of Skin Cancer

Melanoma is, by far, the most deadly type of skin cancer. It is most often a result of exposure to ultraviolet (UV) rays — whether from the sun, sun lamps, or tanning beds . A melanoma often looks like a mole. It is usually black or brown but it can also be skin-colored, purple, blue, red, pink, or white.

Learn More About Melanoma

Some skin cancers closely resemble normal skin or a harmless mole, but there can also be signs of danger. One red flag for basal cell and squamous cell carcinoma is an open sore that repeatedly bleeds and crusts. These cancers could also look like a pink bump with raised edges and a depression in the center; or they can resemble pink, reddish, or brown patches that lie flat against the skin. Melanoma, the most dangerous cancer, has subtle differences that can help distinguish it from a benign mole: It might be asymmetrical, for instance, or have notched edges instead of smooth ones. Knowing these differences — and conducting regular skin checks to identify suspicious growths — can lead to early detection and the best possible outcome after treatment.

Learn More About the Signs and Symptoms of Skin Cancer

If you have skin cancer, the treatment you’ll get will depend on a number of things, starting with the type of cancer and its severity. Surgery — usually outpatient, under local anesthesia — is often the first step. For a small, superficial, low-risk basal cell carcinoma, a dermatologist might scrape off the tumor using a device called a curette. A bigger or trickier cancer might call for Mohs surgery, during which the doctor methodically removes the cancer layer by layer, examining each under a microscope for any stray cancer cells. Excisional surgery, in which the doctor uses a scalpel to remove the entire tumor as well as a margin of healthy skin around it, may be the best choice for many patients, with newer techniques resulting in smaller scars.

There are also forms of superficial radiation treatment that are effective for skin cancer. Radiation requires multiple treatments but may help patients at high risk for surgical complications. Radiation may also help prevent surgical scarring in some individuals

Learn More About Skin Cancer Treatment