Overview illustration for skin cancer

Skin Cancer Overview

Nonmelanoma skin cancer is the most common type of cancer. This type of skin cancer is usually not life threatening, but it should be treated promptly. There are two main types: squamous cell carcinoma and basal cell carcinoma. Symptoms can include a bump that is red or pearly white, or a patch of skin that bleeds, crusts over, or doesn't heal.

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Of all the cancers of the human body, skin cancer is the most common. One in five Americans will develop it in their lifetime.

Skin cancer is generally divided into two main categories:

The most common is nonmelanoma skin cancer, and its two main types—basal cell carcinoma and squamous cell carcinoma—are highly curable, if detected and treated early. Symptoms can include a red, pearly white, or darkly pigmented bump (depending on your skin color) or a patch of skin that bleeds, crusts over, or doesn't heal.

Melanoma is the less common and more dangerous form of skin cancer. A typical melanoma may appear as a mole that changes in shape, size, or color. Others may look like a bruise that doesn't heal or a dark streak under a fingernail or toenail.

What Is It

Skin cancer is an uncontrolled growth of abnormal skin cells in skin tissue. It usually starts in squamous or basal cells that reside in the skin's outer layer, called the epidermis. It can also begin in pigment-making cells known as melanocytes.

You may have heard that fair-skinned folks are particularly vulnerable. But skin pigmentation is just one variable. People of all skin tones may develop skin cancer, even if their skin is darker or they rarely burn. A majority of skin cancer cases and deaths are due to excessive ultraviolet (UV) radiation exposure from the sun or tanning beds. So if you're someone who spends a lot of time out in the sun without sun protection, you may be at greater risk of developing this cancer.

The type of skin cancer someone has and how early it is detected will determine the course of treatment and prognosis.


Skin cancers differ by the type of cell affected. These are the most common skin cancers:

Basal cell carcinoma. This tends to be a slow-growing cancer and it accounts for roughly 80% of all skin cancers. It starts in the small, round basal cells of the innermost layer of the epidermis.

Squamous cell carcinoma. This is the second most common type of skin cancer. It develops in the flat, fish-scale-shaped cells located above the basal cell layer of the epidermis.

Melanoma skin cancer. This is the most serious form of skin cancer. Melanoma arises from melanocytes, the skin's pigment-producing cells.

Merkel cell cancer (aka neuroendocrine carcinoma of the skin) is an uncommon skin cancer that develops in sensory cells, called Merkel cells, that reside in the deepest layer of the epidermis. It is among a group of rare cancers of the skin (including cutaneous lymphoma, Kaposi sarcoma, and others), which together account for just 1% of all skin cancers.


Skin cancer usually develops on sun-exposed areas of the body—think scalp, face, ears, neck, chest, arms, and hands. That said, it can appear anywhere on the body, even in your genital area. People of color may develop melanoma on the soles of the feet, the palms of the hands, or underneath the nails.What skin cancer looks like varies widely. Look for:

  • a new growth.
  • a sore that won't heal.
  • a mole that changes in shape, size, color, or feel.
  • a brown patch of skin (in people of color).

Each type of cancer has its own features.

Basal cell carcinoma might look like a scar; a raised, reddish patch; a pink, red, or pearly white or pearly black bump; or an open sore.

Squamous cell carcinoma can present as a rough, scaly patch that might bleed or crust; a raised growth, possibly with a depression in the middle; an open sore; or a wart-like lesion.

Melanoma often shows up as a new spot on the skin, one that looks different from all other surrounding spots on the skin—the so-called "ugly duckling." It can also show up in an existing mole. In either case, be aware of any spots or moles. The "ABCDE rule" may help you identify potential melanomas:

  • A for Asymmetry. One half of the spot or mole does not match the other half.
  • B for Border. Its perimeter is ragged.
  • C for Color. It has multiple hues.
  • D for Diameter. Often diagnosed when larger than a pencil eraser, melanomas can be smaller.
  • E for Evolving. It's changing in size, shape, or color.


Most skin cancers are due to overexposure to UV radiation from the sun. Sunlamps and tanning beds are also a source of this form of radiation. UVA rays are known for long-term skin aging (in other words, it makes you wrinkle), while UVB rays are associated with sunburn. UVB can damage the DNA in your skin cells, which is the cause of most skin cancers, although UVA rays are thought to play a role too.

Skin cancers are more common in older people, typically affecting skin-exposed areas of the body. People with weak immune systems are also vulnerable. Of course, skin cancer can also affect skin that doesn't get much sun exposure, and it can occur in young, otherwise healthy people.

Other risk factors include:

  • Lighter skin tone.
  • Skin that easily burns, freckles, reddens, or becomes painful in the sun.
  • Having blue or green eyes.
  • Having blond or red hair.
  • A history of excessive sun exposure or sunburns.
  • A personal or family history of skin cancer.
  • Having certain atypical moles or a large number of moles.


The diagnostic process begin with a medical history (to assess a person's risk factors for skin cancer), a physical exam, and a skin biopsy. The doctor may use a magnifying device called a dermatoscope to evaluate any suspicious skin lesions. If a spot appears unusual, the area will be numbed and your doctor will take a skin sample to send to a lab for examination under a microscope.

The doctor may also feel nearby lymph nodes. Are they larger? Firmer? A lymph node biopsy may be performed to determine if the cancer has spread, especially if melanoma has been diagnosed. (Basal and squamous cell cancers don't usually spread beyond the skin.) Common techniques include:

  • Fine needle aspiration. Extracting a cell sample using a thin needle.
  • Surgical biopsy. Removing the enlarged lymph node.
  • Sentinel lymph node biopsy. Using radiation and blue dye to identify affected lymph nodes and surgically removing them.

Depending on the stage of melanoma, imaging and blood tests may also be performed.


Lots of factors may be weighted when determining the best course of treatment for someone's skin cancer. It may depend on:

  • The type of cancer.
  • Its size.
  • How deeply it has penetrated the skin.
  • Its location.
  • Whether it has spread to other parts of the body.

Treatment options may include:

Surgery. Scraping and burning off the lesion, cutting it out, using laser light to destroy the cancer, or removing a layer of tissue at a time (aka Mohs surgery).

Radiation. Often for cancers that are hard to treat surgically or for tumors that have spread.

Cryotherapy. Freezing the skin cancer with liquid nitrogen.

Chemotherapy. Delivered topically or systemically (i.e. through a vein or by mouth).

Photodynamic therapy. Combining laser light and a topical agent to kill cancer cells.

Topical treatments. Using creams or gels to attack the cancer.

Immunotherapy or targeted therapy. Specialized cancer medicines.


Short of permanently cloistering yourself indoors, there are lots of things you can do to minimize your risk of skin cancer:

  • Seek shade, especially during the midday hours.
  • Wear tightly-knit, dark-colored clothing that covers your arms and legs. You can also wear special apparel that offers sun protection for days when you know you'll be in a lot of sun.
  • Put on a hat with a wide brim to protect your head, face, ears, and neck.
  • Don a pair of UV-protective sunglasses.
  • Slather on a broad-spectrum sunscreen that blocks UVA and UVB rays.
  • Avoid tanning—outdoors or indoors. Don't use tanning beds.
  • Check your skin monthly.
  • Consider having a full-body screening by a dermatologist
  • Get checked out any time you develop a new or suspicious spot on your skin.

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