Actinic Keratosis (Solar Keratosis)

  • Medical Author:
    Gary W. Cole, MD, FAAD

    Dr. Cole is board certified in dermatology. He obtained his BA degree in bacteriology, his MA degree in microbiology, and his MD at the University of California, Los Angeles. He trained in dermatology at the University of Oregon, where he completed his residency.

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

    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

Actinic keratosis facts

  • An actinic keratosis is a small, rough spot occurring on sun-exposed skin.
  • Actinic keratoses are also known as a solar keratoses.
  • 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 very thin superficial lesions that have not penetrated into the deeper layers of the skin; they are predisposed to become skin cancer however.
  • Doctors can usually diagnose an actinic keratosis simply by physical examination.
  • It is best to prevent actinic keratoses 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? What causes actinic keratoses?

An actinic keratosis (AK) is a small, rough spot occurring on skin that develops because of chronic sun exposure. These small superficial spots are superficial skin cancers that have not invaded the deeper layers of the skin. Actinic keratoses characteristically appear on photo-damaged skin. 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).

What are symptoms and signs of an actinic keratosis?

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 Treatment

Photodynamic Therapy

Photodynamic therapy (PDT) is a medical treatment that utilizes a photosensitizing molecule (frequently a drug that becomes activated by light exposure) and a light source to activate the administered drug. Very thin superficial skin cancers called actinic keratoses and certain other types of cancer cells can be eliminated this way. Acne can also be treated as well. The procedure is easily performed in a physician's office or outpatient setting. PDT is also referred to as blue light therapy.

PDT essentially has three steps. First, a light-sensitizing liquid, cream, or intravenous drug (photosensitizer) is applied or administered. Occasionally, a photosensitizing molecule that is already part of the body can be activated. Second, there is an incubation period of minutes to days. Finally, the target tissue is then exposed to a specific wavelength of light that then activates the photosensitizing medication. The mechanism by which tissue is destroyed seems to depend on the presence of activated oxygen molecules.

Who is at risk for actinic keratoses?

Those who develop actinic keratoses tend to be fair-skinned people who have spent years outdoors at work or play or who have exposed their skin to indoor tanning radiation. Their skin often becomes wrinkled, mottled, and thinned from sun exposure. Others at risk include immunosuppressed organ transplant patients and patients treated with PUVA therapy (long-wave ultraviolet light plus an oral drug called psoralen) for psoriasis.

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 or on a bald pate, whereas long hair is often protective.

What is the significance of an actinic keratosis?

Actinic keratoses localized superficial tumors with the biological potential to develop into invasive skin cancer. Although the chance of an individual actinic keratosis progressing into an invasive squamous cell carcinoma is less than 1%, patients with many of these lesions (very common) who continue to expose their skin to carcinogenic ultraviolet sunlight are likely to develop 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 will help prevent invasive skin cancer. When patients are diagnosed with this condition, they often say, "But I never go out in the sun!" The explanation for this 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 actinic keratoses or transform them into skin cancers.

What specialists diagnose actinic keratoses?

Generally, primary care physicians or dermatologists can diagnose and care for actinic keratosis. If the lesion is especially large or thick, a biopsy may be advisable to make sure that the spot in question has not become a skin cancer.

There are other spots, called seborrheic keratoses, which 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.

What is the treatment for an actinic keratosis?

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 with liquid nitrogen
  • Other forms of surgery: Doctors sometimes scrape away or burn off AKs.
  • Laser resurfacing: Using either carbon dioxide (CO) or erbium:yttrium aluminum garnet (Er:YAG) lasers
  • 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 only modest improvement.
  • Superficial chemical peels using trichloracetic acid (TCA) can also be effective. This procedure is performed in the doctor's office.

Quick GuideSun-Damaged Skin: Pictures of Sun Spots, Wrinkles, Sunburns

Sun-Damaged Skin: Pictures of Sun Spots, Wrinkles, Sunburns

Are there home remedies for actinic keratoses?

There are no home remedies for actinic keratoses, but many will resolve spontaneously if sun exposure can be strictly limited. Those lesions that do not resolve need professional medical attention.

Is it possible to prevent actinic keratoses?

Sun avoidance is the simplest way to avoid actinic keratoses. This would include applications of SPF 50 sunscreens to exposed skin, wearing sun-protective clothing, shade-seeking behavior, and avoiding tanning. There is now some evidence that taking niacinamide (nicotinamide), not niacin, may have some preventative benefit. Niacinamide is available at many health food stores. Concerns about vitamin D deficiency can be avoided by taking multivitamin supplements.

What is the prognosis of an actinic keratosis?

Patients who develop actinic keratoses should be examined at least once yearly. Actinic keratoses are an indicator that sufficient sun exposure has occurred to produce skin cancers such as basal cell carcinoma, squamous cell carcinoma, and malignant melanoma. The purpose of these regular checks is to prevent and detect the development of invasive skin cancer. Furthermore, continual avoidance of excessive sun exposure can decrease the risk of recurrences.

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Medically Reviewed on 8/24/2018
References
REFERENCES:

Conforti, Claudio, Emanuela Beninanti, and Caterina Dianzani. "Are Actinic Keratoses Really Squamous Cell Cancer? How Do We Know if They Would Become Malignant?" Clinics in Dermatology (2017). doi: 10.1016/j.clindermatol.2017.08.01.

Costa, Claudia, et al. "How to Treat Actinic Keratosis? An Update." J Dermatol Case Rep 9.2 (2015): 29-35.

Uhlenhake, E.E. "Optimal treatment of actinic keratoses." Clin Interv Aging 8 (2013): 29-35.
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