Actinic Keratosis (Solar Keratosis)

Medical Author : Gary W. Cole, MD, FAAD

Medical Editor : William C. Shiel Jr., MD, FACP, FACR

Actinic keratosis facts

  • An actinic keratosis is a small, rough spot occurring on skin that has been chronically exposed to the sun.
  • Actinic keratosis is also known as a solar keratosis.
  • Actinic keratoses occur most commonly in fair-skinned people after years of sun exposure.
  • Common locations for actinic keratoses are the face, scalp, ears, back of the neck, upper chest, as well as the tops of the hands and forearms.
  • Actinic keratoses are precancerous, which means they can develop into skin cancer.
  • Doctors can usually diagnose an actinic keratosis just by physical examination.
  • The best treatment for an actinic keratoses is prevention by minimizing sun exposure.
  • Treatments for actinic keratoses include cryosurgery, scraping or burning, 5-fluorouracil cream, imiquimod (Aldara), diclofenac (Voltaren, Cataflam, Voltaren-XR, Cambia), ingenol mebutate (Picato), TCA skin peels, and photodynamic therapy.

What is an actinic keratosis, and what does it look like?

An actinic keratosis (AK) is a small, rough spot occurring on skin that develops because of chronic sun exposure. Actinic keratoses generally range in size between 2-6 mm in diameter (between the size of a pencil point and that of an eraser). They are usually reddish in color, with a rough texture and often have a white or yellowish scale on top. There is often a prickling pain felt when it is touched. Actinic keratosis often occurs against a background of sun damage, including sallowness, wrinkles, and excess superficial blood vessels. Actinic keratosis is also referred to as a solar keratosis.

Specialized forms of actinic keratoses include cutaneous horns, in which the skin protrudes in a thick, hornlike manner, and actinic cheilitis, a scaling and roughness of the lower lip and blurring of the border of the lip and adjacent skin. There are other causes of cutaneous horns, including warts and age spots (seborrheic keratoses).

Who is at risk for an actinic keratosis?

Those who develop actinic keratoses tend to be fair-skinned people who have spent a lot of time outdoors at work or at play over the course of many years or who have exposed their skin to indoor tanning radiation. Their skin often becomes wrinkled, mottled, and discolored from sun exposure. Others at risk for developing actinic keratoses include those who have their immune systems suppressed, such as organ-transplant patients, as well as patients with psoriasis treated with PUVA therapy (topical long-wave ultraviolet light plus oral chemicals called psoralens).

Where on the body do actinic keratoses typically occur?

Common locations for actinic keratoses are the cheeks, bridge of the nose, rim of the ears, scalp, back of the neck, upper chest, and the tops of the hands and forearms. Men are more likely to develop AKs on top of the ears, whereas women's hairstyles often protect this area. AKs, especially on the scalp and the backs of the hands, may cause thickened skin.

What is the significance of an actinic keratosis?

Actinic keratoses are precancerous (premalignant), which means they can develop into skin cancer. Even though the chance of an individual actinic keratoses progressing into an invasive squamous cell carcinoma is on the order of less than one percent, most patients have many of these lesions and most continue to expose their skin to carcinogenic ultraviolet sunlight. These facts increase the likelihood for the development of invasive skin cancers Squamous cell skin cancers are locally destructive and have a small but real potential for metastasis (spreading to other areas). Treating actinic keratoses at an early stage may help prevent this from happening.

When patients are diagnosed with this condition, they often say, "But I never go out in the sun!" The explanation is that there can be a long delay, even decades for these keratoses to develop. Short periods of sun exposure do not generally either produce AKs or transform them into skin cancers.

How is an actinic keratosis diagnosed?

Most of the time, doctors can diagnose an actinic keratosis just by examining it. If the AK is especially large or thick, a biopsy may be advisable to make sure that the spot in question is just a keratosis and has not become a skin cancer.

There are other spots, called seborrheic keratoses, that are not caused by sun exposure and have no relationship to skin cancers. These are raised brown lesions that may appear on any area of the skin. They also often run in families.

How is an actinic keratosis treated?

The best treatment for an AK is prevention. For light-skinned individuals, this means minimizing their sun exposure. By the time actinic keratoses develop, however, the relevant ultraviolet radiation is often so far in the past that prudent preventive measures play a relatively small role. Fortunately, treatment methods are usually simple and straightforward:

  • Cryosurgery: Freezing AKs with liquid nitrogen often causes them to slough off and go away.
  • Other forms of surgery: Doctors sometimes scrape away or burn off AKs.
  • 5-fluorouracil (5-FU): Creams containing this medication cause AKs to become red and inflamed before they fall off. Although effective, this method often produces unsightly and uncomfortable skin for a period of weeks, thus making it impractical for many patients. This method is best for patients who have a great deal of sun damage and many AKs. Once the skin heals, it often looks much smoother and even-toned.
  • Imiquimod (Aldara): This immune stimulator is similar in its indications and effects to 5-FU.
  • Ingenol mebutate (Picato): Is derived from the sap of a plant of the genus Euphorbia, which is related to the poinsettia plants that are popular at Christmas time. It is helpful in the treatment of small areas, but causes significant irritation.
  • Photodynamic therapy (PDT): This therapy involves applying an agent (aminolevulinic acid [Levulan] or ALA) that sensitizes the skin to light, leaving it on for about one hour, and then exposing the skin to light that activates the chemical. This blue light is absorbed by the compound, releasing the energy as heat which is believed to destroy the actinic keratoses. Like 5-FU and imiquimod, photodynamic therapy works best for patients with many AKs. Patients need to avoid exposure to sun or intense fluorescent light for two days after treatment to prevent ongoing peeling.
  • Diclofenac (Solaraze): This cream is a nonsteroidal anti-inflammatory drug (NSAID), an agent related to ibuprofen (Advil, Children's Advil/Motrin, Medipren, Motrin, Nuprin, PediaCare Fever), a popular medication for headaches. Diclofenac is gentler than 5-FU or imiquimod, causing less inflammation, but must be applied for a longer period of about two months to achieve modest improvement.
  • Superficial chemical peels using trichloracetic acid (TCA) can also be effective. This procedure is performed in the doctor's office.

    What happens after an actinic keratosis is treated?

    Patients who develop actinic keratoses are usually well advised to have a doctor examine them annually. The purpose of these regular checks is to be sure that new lesions have not developed and that old ones are not becoming thicker and more suspicious looking (for cancer). Furthermore, continual avoidance of excessive sun exposure can decrease the risk of recurrences.

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