Skin cancer is an abnormal growth of skin cells. It generally develops in areas that are exposed to the sun, but it can also form in places that don’t normally get sun exposure.

The two main categories of skin cancers are defined by the cells involved.

Keratinocyte carcinoma

The first category is basal and squamous cell skin cancers. These are the most common forms of skin cancer. They’re most likely to develop on areas of your body that get the most sun, like your head and neck.

They’re less likely than other forms of skin cancer to spread and become life-threatening. But if left untreated, they can grow larger and spread to other parts of your body.

Melanoma

The second category of skin cancers is melanoma. This type of cancer develops from cells that give your skin color. These cells are known as melanocytes. Benign moles formed by melanocytes can become cancerous.

They can develop anywhere on your body. In men, these moles are more likely to develop on the chest and back. In women, these moles are more likely to develop on the legs.

Most melanomas can be cured if they’re identified and treated early. If left untreated, they can spread to other parts of your body and become harder to treat. Melanomas are more likely to spread than basal and squamous cell skin cancers.

Skin moles and lesions that could be cancer often resemble spots that are not cancerous at all. Use these pictures of skin cancer as a guide to compare any spots on your body, but see a dermatologist for a proper diagnosis.

Two main types of skin masses exist, keratinocyte carcinoma and melanoma. However, several other skin lesions are considered part of a larger skin cancer umbrella. Not all of these are skin cancer, but they can become cancerous.

  • Actinic keratosis: These red or pink patches of skin are not cancerous, but they’re considered a form of precancer. If left untreated, these skin masses may develop into squamous cell carcinoma.
  • Basal cell carcinoma: The most common form of skin cancer, basal cell carcinomas account for of all cases of skin cancer. They’re slow-growing masses that most often show up on the head or neck.
  • Squamous cell carcinoma: This type of skin cancer develops in the outer layers of your skin, and it’s typically more aggressive than basal cell carcinoma. It may show up as red, scaly lesions on your skin.
  • Melanoma: This type of skin cancer is less common, but it’s the most dangerous type of skin cancer. In fact, melanoma makes up just of skin cancers, but it causes the majority of skin cancer-related deaths each year. Melanoma forms in the melanocytes, the skin cells that create pigment.

Some skin cancer types are more common than others. Read more about each type to understand why they form and what they may look like.

Skin cancers aren’t all identical, and they may not cause many symptoms. Still, unusual changes to your skin can be a warning sign for the different types of cancer. Being alert for changes to your skin may help you get a diagnosis earlier.

Watch out for symptoms, including:

  • skin lesions: A new mole, unusual growth, bump, sore, scaly patch, or dark spot develops and doesn’t go away.
  • asymmetry: The two halves of the lesion or mole aren’t even or identical.
  • border: The lesions have ragged, uneven edges.
  • color: The spot has an unusual color, such as white, pink, black, blue, or red.
  • diameter: The spot is larger than one-quarter inch, or about the size of a pencil eraser.
  • evolving: You can detect that the mole is changing size, color, or shape.

If you think you have a spot on your skin that may be a skin cancer, know all the possible warning signs.

Both types of skin cancer occur when mutations develop in the DNA of your skin cells. These mutations cause skin cells to grow uncontrollably and form a mass of cancer cells.

Basal cell skin cancer is caused by ultraviolet (UV) rays from the sun or tanning beds. UV rays can damage the DNA inside your skin cells, causing the unusual cell growth. Squamous cell skin cancer is also caused by UV exposure.

Squamous cell skin cancer can also develop after long-term exposure to cancer-causing chemicals. It can develop within a burn scar or ulcer, and may also be caused by some types of human papillomavirus (HPV).

The cause of melanoma is unclear. Most moles don’t turn into melanomas, and researchers aren’t sure why some do. Like basal and squamous cell skin cancers, melanoma can be caused by UV rays. But melanomas can develop in parts of your body that aren’t typically exposed to sunlight.

Your recommended treatment plan will depend on different factors, like the size, location, type, and stage of your skin cancer. After considering these factors, your healthcare team may recommend one or more of the following treatments:

  • cryotherapy: The growth is frozen using liquid nitrogen and the tissue is destroyed as it thaws.
  • excisional surgery: The growth and some of the healthy skin surrounding it are cut out.
  • Mohs surgery: The growth is removed layer by layer, and each layer is examined under a microscope until no abnormal cells are visible.
  • curettage and electrodessication: A long spoon-shaped blade is used to scrape away the cancer cells, and the remaining cancer cells are burned using an electric needle.
  • chemotherapy: Drugs are taken orally, applied topically, or injected with a needle or IV line to kill the cancer cells.
  • photodynamic therapy: A laser light and drugs are used to destroy the cancer cells.
  • radiation: High-powered energy beams are used to kill the cancer cells.
  • biological therapy: Biological treatments are used to stimulate your immune system to fight the cancer cells.
  • immunotherapy: A cream is applied to your skin to stimulate your immune system to kill the cancer cells.

Ask your doctor for more information about your treatment options.

If you develop suspicious spots or growths on your skin, or you notice changes in existing spots or growths, make an appointment with your doctor. You doctor will examine your skin or refer you to a specialist for diagnosis.

Your doctor or specialist will likely examine the shape, size, color, and texture of the suspicious area on your skin. They will also check for scaling, bleeding, or dry patches. If your doctor suspects it might be cancerous, they may perform a biopsy.

During this safe and simple procedure, they will remove the suspicious area or a portion of it to send to a lab for testing. This can help them learn if you have skin cancer.

If you’re diagnosed with skin cancer, you may need additional tests to learn how far it has progressed. Your recommended treatment plan will depend on the type and stage of your skin cancer, as well as other factors.

A skin cancer screening performed by your dermatologist is a quick and easy procedure. You will be asked to remove your clothes down to your underwear and wear a thin, paper robe.

When your doctor comes into the room, they will examine every inch of your skin, noting any unusual moles or spots. If they see anything questionable, they will discuss next steps with you at this point.

Early detection is the best way to ensure successful treatment of skin cancer before it develops further. Unlike other organs, your skin is highly visible to you at all times. That means you can proactively watch for signs of changes, unusual spots, or worsening symptoms.

You can follow a self-examination regimen that will help you check every part of your body, even parts that are not exposed to sun. Melanoma is particularly prone to developing in areas that aren’t commonly exposed to the sun. So it’s important you check places like your head and neck as well as between your toes and in your groin.

A skin cancer self-examination takes less than 10 minutes.

To determine a skin cancer’s stage or severity, your doctor will factor in how large the tumor is, if it has spread to your lymph nodes, and if it has spread to other parts of the body.

Skin cancers are divided into two primary groups for staging purposes: nonmelanoma skin cancer and melanoma.

Nonmelanoma skin cancers include basal cell and squamous cell cancers.

  • Stage 0: The abnormal cells have not spread beyond the outermost layer of skin, the epidermis.
  • Stage I: The cancer may have spread to the next layer of skin, the dermis, but it is no longer than two centimeters.
  • Stage II: The tumor is larger than two centimeters, but it has not spread to nearby sites or lymph nodes.
  • Stage III: The cancer has spread from the primary tumor to nearby tissue or bone, and it is larger than three centimeters.
  • Stage IV: The cancer has spread beyond the primary tumor site to lymph nodes and bone or tissue. The tumor is also larger than three centimeters.

Melanoma stages include:

  • Stage 0: This noninvasive type of skin cancer has not penetrated below the epidermis.
  • Stage I: The cancer may have spread to the second layer of skin, the dermis, but it remains small.
  • Stage II: The cancer has not spread beyond the original tumor site, but it is larger, thicker, and may have other signs or symptoms. These include scaling, bleeding, or flaking.
  • Stage III: The cancer has spread or metastasized to your lymph nodes or to nearby skin or tissue.
  • Stage IV: The most advanced stage of melanoma. Stage IV is an indication the cancer has spread beyond the primary tumor and is showing up in lymph nodes, organs, or tissue distant from the original site.

When cancer comes back after treatment, it’s called recurrent skin cancer. Anyone who has been diagnosed with and treated for skin cancer is at risk for a recurrence of the cancer. That makes follow-up care and self-examinations even more important.

To lower your risk of skin cancer, avoid exposing your skin to sunlight and other sources of UV radiation for extended periods of time. For example:

  • Avoid tanning beds and sun lamps.
  • Avoid direct sun exposure when the sun is strongest, from 10 a.m. to 4 p.m., by staying indoors or in the shade during those times.
  • Apply sunscreen and lip balm with a sun protection factor (SPF) of 30 or higher to any exposed skin at least 30 minutes before heading outdoors and reapply regularly.
  • Wear a wide-brimmed hat and dry, dark, tightly woven fabrics when you’re outside during daylight hours.
  • Wear sunglasses that offer 100 percent UVB and UVA protection.

It’s also important to regularly examine your skin for changes like new growths or spots. Tell your doctor if you notice anything suspicious.

If you develop skin cancer, identifying and treating it early can help improve your long-term outlook.

Nonmelanoma skin cancer refers to skin cancers that are not melanoma. This type of skin cancer includes:

While these cancers can grow larger and spread beyond the original tumor site, they’re not as fatal as melanoma. Melanoma makes up only of skin cancers diagnosed in America, but it accounts for the majority of skin cancer-related deaths.

Skin cancer is the most commonly diagnosed cancer in America today. More than people are diagnosed with this type of cancer each year.

However, the exact number of skin cancer cases is not known. Many individuals are diagnosed with basal cell or squamous cell carcinomas each year, but doctors are not required to report these cancers to cancer registries.

Basal cell carcinoma is the most common form of skin cancer. Each year, more than cases of this type of nonmelanoma skin cancer are diagnosed. An additional individuals are diagnosed with squamous cell carcinoma.

Invasive melanoma makes up just of all skin cancer cases, but it’s the deadliest form of skin cancer. More than of men and women will be diagnosed with melanoma at some point during their lifetimes.

Each year, doctors diagnose more than new cases of melanoma. More than individuals with melanoma die as a result of their skin cancer.

In 2018, the American Cancer Society estimates Californians will be diagnosed with melanoma, the most of any state. Melanoma is more frequently diagnosed in non-Hispanic whites.

Women are more likely to be diagnosed with melanoma than men during their lifetimes. However, by age 65, men are diagnosed with melanoma at the rate of women. By 80, men are more likely to be diagnosed with melanoma than women.

Almost of nonmelanoma skin cancers could be avoided if people protected their skin from UV radiation. That means more than skin cancer cases could be prevented if people protected their skin from sun exposure and avoided tanning devices and sources of artificial UV light.

Learn more about how common skin cancer is and other important statistics.

Certain factors raise your risk of developing skin cancer. For example, you’re more likely to get skin cancer if you:

  • have a family history of skin cancer
  • are exposed to certain substances, like arsenic compounds, radium, pitch, or creosote
  • are exposed to radiation, for example during certain treatments for acne or eczema
  • get excessive or unprotected exposure to UV rays from the sun, tanning lamps, tanning booths, or other sources
  • live or vacation in sunny, warm, or high-altitude climates
  • work outdoors frequently
  • have a history of severe sunburns
  • have multiple, large, or irregular moles
  • have skin that’s pale or freckled
  • have skin that sunburns easily or doesn’t tan
  • have natural blond or red hair
  • have blue or green eyes
  • have precancerous skin growths
  • have a weak immune system, for example from HIV
  • have had an organ transplant and take immunosuppressant medication

If you’re diagnosed with skin cancer, your doctor may assemble a team of specialists to help address different aspects of your condition. For example, your team may include one or more of the following:

  • a dermatologist who treats skin diseases
  • a surgical oncologist who treats cancer using surgery
  • a radiation oncologist who treats cancer using radiation therapy
  • a medical oncologist who treats cancer using targeted therapy, immunotherapy, chemotherapy, or other medications

You may also receive support from other healthcare providers, such as:

  • nurses
  • nurse practitioners
  • physician assistants
  • social workers
  • nutrition specialists

Potential complications of skin cancer include:

  • recurrence, where your cancer comes back
  • local recurrence, where cancer cells spread to surrounding tissues
  • metastasis, where cancer cells spread to muscles, nerves, or other organs in your body

If you’ve had skin cancer, you’re at heightened risk of developing it again in another location. If your skin cancer recurs, your treatment options will depend on the type, location, and size of the cancer, and your health and prior skin cancer treatment history.