Precancer: Actinic Keratosis and Atypical Moles

Reviewed by: HU Medical Review Board | Last reviewed: May 2017.

Actinic keratosis is a type of precancer, which is an abnormality that can lead to cancer. These lesions form when cells in the top layer of skin begin to grow abnormally.1

What is actinic keratosis

Actinic keratoses look like a rough, scaly patch that range in color from normal skin to reddish brown.2 Sometimes these lesions itch or burn, but most do not cause any symptoms.2 The lesions generally appear on skin that has been exposed to sun. Another name for actinic keratosis is “solar keratosis.”

Most actinic keratoses do not become cancer. In fact, about 25% of these lesions will clear up on their own within a year.1 However, between 6% and 10% of actinic keratoses will spread into the dermis layer of skin. When they do, they become squamous cell carcinoma (SCC).2

Who develops actinic keratosis?

Actinic keratoses become more common with age. An estimated 6 out of 10 people older than 40 years have at least one actinic keratosis.2 People with fair skin and blue eyes are particularly at risk.2

What are the treatments for actinic keratosis?

The reason for treating actinic keratosis is to stop the lesion from progressing to SCC. Many treatments are available. The best treatment will depend on how many lesions you have and where they are located. Sometimes, these treatments are used together. Luckily, most actinic keratoses can be addressed when treated early.3

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Cryotherapy is the most common treatment for actinic keratosis.2 This treatment works best when there are only a few lesions that are clearly defined. Your health care provider will spray or swab liquid nitrogen on the lesion. The nitrogen freezes the lesion. This procedure is done in the office. Serious side effects are rare.2 You may feel burning or discomfort in the place that was treated. The treated spot may turn white; sometimes the discoloration improves over several months, but it can be permanent.4 You may have permanent hair loss in the treated area and long-term (12 to 18 months) loss of sensation.4

Topical medications

Actinic keratoses can be treated with medications that are applied directly to the skin. Topical medications are useful for people who have many lesions. These medications include:

  • Fluorouracil (5-FU)
  • Imiquimod
  • Diclofenac
  • Ingenol mebutate

These medications are applied to the affected area once or twice a day. Treatment with topical medications may take as little as 2 days or up to several months to work, depending on the medication used. Side effects vary by medication. They include redness, dry skin, and irritation in the treated areas.

Facial chemical peel may be an alternative to topical medications. Chemical peels can be done in a single visit.2

Photodynamic therapy

Photodynamic therapy is used to treat numerous lesions on the face and scalp.2 A light-sensitizing agent is applied to the lesions. Hours later, the lesions are exposed to a strong blue or red light that destroys the abnormal cells. Side effects include redness and swelling, burning, and pain. The skin at the treatment site may crust over, change color, or become scaly.2 After this procedure, you must stay out of the sun for at least two days.5


This treatment may be useful if your health care provider also wants to have a tissue sample from the actinic keratosis. The abnormal tissue is scraped away using a tool called a curette. Your doctor will provide local anesthesia before this procedure. Possible side effects include infection, scarring, and change in skin color.2

What are atypical moles?

Nearly all adults have moles. Most are common moles that will never cause a problem.6 Common moles may appear anywhere on the body.7 They usually are evenly colored with one to two shades of brown. Common moles are small, round or oval, and symmetrical.

Atypical moles are larger than common moles. They are not melanoma, but they look like melanoma. They may be 6 millimeters (mm) or more—larger than a pencil eraser. The color of the mole may be a mix of tan, brown, red, and pink.6,7 The border of the mole may not be well defined and it may appear pebbled. Atypical moles are most common on the torso, scalp, or neck.6 Other names for atypical moles are “dysplastic nevi” or “atypical nevi.”

Atypical moles are benign, which means they are not cancerous. Most melanomas do not develop from existing atypical moles.7 However, people with five or more atypical moles have a higher risk of developing skin cancer in their lifetime than people with fewer atypical moles.7,8

Who has atypical moles?

About 2% to 8% of fair-skinned people have atypical moles. They are much less common in people with darker skin tones.7

Atypical moles can run in families. This can be due to “familial atypical multiple mole-melanoma syndrome” or FAMMM. People with FAMMM usually have more than 50 moles—some of which are atypical—and a blood relative who has had melanoma.6,9 Nearly everyone with FAMMM will develop melanoma during his or her lifetime.7

When should I see a doctor about atypical moles?

It is important to watch for changes in existing moles and the appearance of new moles. Atypical moles are not melanoma; however, the ABCDE memory aid can help you to identify suspicious moles:7

  • Asymmetry
  • Border irregularity
  • Color unevenness
  • Diameter of 6 mm or more
  • Evolution or changes in the mole

Talk to your dermatologist or primary care provider about new or changing lesions. Your dermatologist may recommend regular screenings to keep an eye on suspicious moles. Your dermatologist will do a physical exam and may take photographs of your lesions. If your dermatologist thinks that the lesion might be melanoma, she or he will do a skin biopsy and look at a sample of cells in the lab.