Solar/Actinic Keratosis: What You Should Know About This Common Precancer

You have surely seen an actinic keratosis. The name may be unfamiliar, but the appearance is commonplace. Anyone who spends time in the sun runs a high risk of developing one or more.

What is it?

An actinic keratosis (AK), also known as a solar keratosis, is a scaly or crusty bump that arises on the skin surface. The base may be light or dark, tan, pink, red, or a combination of these. . . or the same color as your skin. The scale or crust is horny, dry, and rough, and is often recognized by touch rather than sight. Occasionally it itches or produces a pricking or tender sensation. It can also become inflamed and surrounded by redness. In rare instances, actinic keratoses can even bleed.

The skin abnormality or lesion develops slowly and generally reaches a size from an eighth to a quarter of an inch. Early on, it may disappear only to reappear later. You will often see several AKs at a time.

An AK is most likely to appear on the face, ears, scalp, neck, backs of the hands and forearms, shoulders, and lips - the parts of the body most often exposed to sunshine. The growths may be flat and pink or raised and rough.

Why is it dangerous?

AK can be the first step in the development of skin cancer. It is thus a precursor of cancer or a precancer.

If treated early, almost all AKs can be eliminated without becoming skin cancers. But untreated, about two to five percent of these lesions may progress to squamous cell carcinomas. In fact, some scientists now believe that AK is the earliest form of SCC. These cancers are usually not life-threatening, provided they are detected and treated in the early stages. However, if this is not done, they can grow large and invade the surrounding tissues and, on rare occasions, metastasize or spread to the internal organs.

Another form of AK, actinic cheilitis, develops on the lips and may evolve into a type of SCC that can spread rapidly to other parts of the body.

If you have AKs, it indicates that you have sustained sun damage and could develop any kind of skin cancer - not just squamous cell carcinoma. The more
keratoses that you have, the greater the chance that one or more may turn into skin cancer. People may also have up to 10 times as many subclinical (invisible) lesions as visible, surface lesions.

What does it look like?

Common forms of actinic keratoses are shown here in the locations where they most often develop. Examine your skin to find any lesions that look like these. if you spot them, consult your doctor promptly.

What is the cause?

Chronic sun exposure is the cause of almost all AKs. Sun damage to the skin accumulates over time, so that even a brief exposure adds to the lifetime total.

The likelihood of developing AK is highest in regions near the equator. However, regardless of climate, everyone is exposed to the sun. About 80 percent of solar UV rays can pass through clouds. These rays can also bounce off sand, snow, and other reflective surfaces, giving you extra exposure.

AKs can also appear on skin that has been frequently exposed to artificial sources of UV light (such as tanning devices). More rarely, they may be caused by extensive exposure to X-rays or specific industrial chemicals.

Who is at greatest risk?

People who have fair skin, blonde or red hair, and/or blue, green, or gray eyes are at greatest risk. Because their skin has little protective pigment, they are most susceptible to sunburn. But even darker-skinned people can develop AKs if exposed to the sun without protection.

Individuals whose immune systems are weakened as a result of cancer chemotherapy, AIDS, or organ transplantation are also at higher risk.

How common is it?

AK is the most common type of precancerous skin lesion. Older people are more likely than younger ones to develop these lesions, because cumulative sun exposure increases with the years. Some experts believe that the majority of people who live to the age of 80 will have AK.

On average, however, more than half of our lifetime sun exposure occurs before age 20. Thus, AKs also appear in people in their early twenties who have spent too much time in the sun with little or no protection.

How is it treated?

There are many effective methods for eliminating AKs. All cause a certain amount of reddening, and some may cause scarring, while other approaches are less likely to do so. You and your doctor should decide together the best course of treatment, based on the nature of the lesion and your age and health.

Cryosurgery

The most common treatment for AK, it is especially effective when a limited number of lesions exist. No cutting or anesthesia are required. Liquid nitrogen is applied to the growths with a spray device or cotton-tipped applicator to freeze them. They subsequently shrink or become crusted and fall off. Some temporary swelling may occur after treatment, and in dark-skinned patients, some pigment may be lost.

Curettage and Desiccation

This is a valuable procedure for lesions suspected to be early cancers. To test for malignancy, the physician takes a biopsy specimen, either by shaving off the top of the lesion with a scalpel or scraping it off with a curette. Then the curette is used to remove the base of the lesion. Bleeding is stopped with an electrocautery needle, and local anesthesia is required.

Topical Medications

Medicated creams and solutions are especially useful in removing both visible and invisible AKs when the lesions are numerous. The patient applies the medication according to a schedule worked out by the physician. The doctor will also regularly check progress. After treatment, some discomfort may result from skin breakdown.

5-fluorouracil (5-FU) cream or solution, in concentrations from 0.5 to 5 percent, is the most widely used topical treatment for AK. It works especially well on the face, ears, and neck. Some swelling and crusting may occur.

For those who are oversensitive to 5-FU or other topical treatments, a gel combining hyaluronic acid and the anti-inflammatory drug diclofenac also may prove effective.

Another preparation, imiquimod cream is also being used by physicians for multiple keratoses. FDA-approved as a genital wart treatment, it causes cells to produce interferon, a chemical that destroys cancerous and precancerous cells.

Chemical Peeling

This method makes use of trichloroacetic acid (TCA) or a similar agent applied directly to the skin. The top skin layers slough off, usually replaced within seven days by new epidermis (the skin's outermost layer). This technique requires local anesthesia and can cause temporary discoloration and irritation.

Laser Surgery

A carbon dioxide or erbium YAG laser is focused onto the lesion, removing epidermis and different amounts of deeper skin. This finely controlled treatment is a good option for lesions in small or narrow areas; it can be particularly effective for keratoses on the face and scalp, as well as actinic cheilitis on the lips. However, local anesthesia may be necessary, and some pigment loss can occur.

Photodynamic Therapy (PDT)

PDT may be used to treat lesions on the face and scalp. Topical 5-aminolevulinic acid (5-ALA) is applied to the lesions by the physician. The next day, the medicated areas are exposed to strong light, which activates the 5-ALA. The treatment selectively destroys actinic keratoses, causing little damage to surrounding normal skin, although some swelling often occurs.

How To Prevent It

The best way to prevent actinic keratosis is to protect yourself from the sun. The Skin Cancer Foundation recommends that these sun safety habits be part of everyone's daily health care:

• Avoid unnecessary sun exposure, especially during the sun's peak hours (10 AM to 4 PM).
   
• Seek the shade.
   
• Cover up with clothing, including a broad-brimmed hat, long pants, a long-sleeved shirt, and UV-blocking sunglasses.
• Wear a broad-spectrum sunscreen with a sun protection factor (SPF) of 15 or higher.
• Avoid tanning parlors and artificial tanning devices.
• Keep newborns out of the sun. Sunscreens can be used on babies over the age of six months.
• Teach children good sun-protective practices.
• Examine your skin from head to toe once every month.
• Have a professional skin examination annually