Skin cancer is caused by the abnormal growth of skin cells—and often develops on areas of the skin exposed to sunlight. The ultraviolet radiation of the sun—as well as tanning beds—has been shown to cause many different types of skin cancer. Family history and genetics can also play a part. As the mutated cells rapidly grow and multiply, they can develop into both malignant and benign tumors. Skin cancer can often be detected in a pre-cancerous stage—before it penetrates below the surface of the skin or becomes a full-blown skin cancer.

Basal cell and squamous cell carcinomas are the most common—and the most treatable—forms of skin cancer. Together, they account for 5.4 million cases in the United States per year, according to the American Cancer Society. And in many cases, these are preventable through being careful about sun exposure. Melanoma, while not as common, is a much more serious form of skin cancer. These three types of skin cancer start in the top layer of the skin, called the epidermis.

While skin cancer commonly develops on areas exposed to the sun, it can also form on areas that rarely get exposed to sunlight, such as your palms, beneath your fingernails and toenails, and your genital area. People of all skin tones can develop skin cancer—including those with darker complexions. For those with darker skin tones, skin cancers are more likely to occur in areas not exposed to the sun, such as the palms of the hands or soles of the feet.

Basal Cell Carcinoma

Basal cell carcinoma is the most common form of skin cancer, and accounts for 80 percent of all cases. Basal cell carcinomas usually form on the sun-exposed areas of the face, head, and neck. They grow very slowly and rarely spread to other parts of the body. However, if they are left untreated, they may spread to the bones or other tissue beneath the skin. If not completely removed, a basal cell carcinoma can come back in the same place on the skin. People who have had basal cell carcinoma are also more likely to develop it in other places on the body.

Squamous Cell Carcinoma

Squamous cell carcinomas account for about 20 percent of skin cancer cases. Squamous cells are flat cells in the outermost layer of the epidermis that constantly renew and shed from the outer layers of the skin. Squamous cell carcinomas usually develop on sun-exposed areas such as the face, ears, neck, lips, and backs of the hands. They can also develop in scars or chronic skin sores. Squamous cell carcinomas can usually be removed completely or treated in other ways. However, they are more likely to spread into the deeper layers of skin and other areas of the body than basal cell carcinoma.

Melanoma

This dangerous skin cancer is responsible for 9,000 deaths in the United States each year. This type of cancer starts in the melanocytes, which are cells that make the brown pigment called melanin. Melanin is the body’s natural sunscreen, protecting the deeper layers of the skin from the harmful effects of the sun. Though melanoma is less common than other skin cancers, it’s more likely to spread to other parts of the body if not treated early.

A melanoma could present as changes to an existing mole, or the appearance of a new one, so be sure to tell your doctor if you see any skin changes.

The Kimberly and Eric J. Waldman Melanoma and Skin Cancer Center is home to the field’s leading specialists, who are highly skilled in caring for the following types of melanoma:

• Superficial spreading melanoma
• Nodular melanoma
• Lentigo maligna melanoma
• Acral lentiginous melanoma

Other Skin Disorders and Precancerous Conditions

The Center treats the full range of skin disorders and precancerous conditions. Actinic keratosis is a precancerous condition that is best treated early. Cutaneous lymphomas and skin cancers related to organ transplants require a team approach—and our physicians coordinate seamlessly with other specialists throughout the Mount Sinai Health System as needed.

Actinic Keratosis

Actinic keratosis is a precancerous condition caused by sun exposure. They often appear as small dry, scaly, or crusty patches of skin. Because of their rough texture, actinic keratoses are often easier to feel than see. Actinic keratosis develops into squamous cell carcinoma about 5 to 10 percent of the time. It is best to see a dermatologist and have actinic keratosis treated early before it becomes cancerous.

Cutaneous T Cell and B Cell Lymphomas

Cutaneous lymphoma is a rare type of cancer that begins in white blood cells called T cells or B cells. White blood cells protect our bodies from invading bacteria, viruses, or toxins, or destroy the body’s own cells that have been taken over by viruses or have become cancerous. While cutaneous lymphoma is technically not a cancer originating in the skin, the T cells or B cells develop abnormalities that cause them to appear primarily in the skin, where they can manifest as a rash or as tumors.

Skin Cancer Related to Transplant

Organ transplants are becoming more and more common. And while these life-saving operations give new hope to patients, they are not without risks. Transplant patients need to take medications that suppress the immune system so that the body doesn’t reject the donor organ. As a result, transplant patients have a higher risk of developing certain types of skin cancer. The most common skin cancers these patients develop are squamous cell carcinoma, basal cell carcinoma, and melanoma, in that order. The risk of squamous cell carcinoma is about 100 times higher than that of the general population. The risk of developing melanoma is about twice that of the general population, according to the Skin Cancer Foundation.