30 Actinic Keratosis (Solar Keratosis)
CLINICAL APPLICATION QUESTIONS
A 65-year-old white man is seen at your office for multiple scaling lesions over his face, ears, neck, and the V of the chest. These have developed gradually over several years.
He is an outdoor sportsman. He is concerned about the character and potential of these lesions, and would like to have them removed because they are itchy and irritable.
Physical examination of the involved regions reveals multiple actinic keratoses (AKs).
Careful examination reveals no lesions that appear overtly malignant.
1. What are the primary lesions that you would expect to find in actinic keratoses?
2. What are the secondary lesions that you would expect to find in actinic keratoses?
3. What should you tell the patient about actinic keratoses?
4. How should you treat actinic keratoses in this patient?
APPLICATION GUIDELINES
Specific HistoryOnset
This type of keratosis is seen with increased incidence in patients from the fifth decade of life onward. The individual lesions begin insidiously as erythematous patches of vasodilation that are often more apparent after solar exposure. Early lesions are usually otherwise asymptomatic.
Evolution of Disease Process
AKs develop after a long latency period (one to two decades), and are caused prima- rily by solar radiation in the UVB or sunburn range from 2900 to 3200 Å. They occur in groupings and are limited to sun-exposed skin. The early erythematous lesions can progress to forms that (1) scale (keratotic type), (2) thicken dramatically (cutaneous horn type), (3) develop a brown branny scale (pigmented type), or (4) become violaceous, slightly indurated, and inflamed to resemble papules of lichen planus (lichenoid type). The last type is uncommon and probably represents an AK with an immune response aimed at rejection. These more developed forms are often mildly symptomatic and patients will complain of intermittent itching and prickling, especially after solar exposure. Following a lengthy latent period some AKs evolve into squamous cell carcinomas, usually of low metastatic potential. Patients will occasionally report spontaneous clearing of specific lesions, possibly a consequence of the histologic changes seen in the lichenoid type.
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From: Current Clinical Practice: Dermatology Skills for Primary Care: An Illustrated Guide D.J. Trozak, D.J. Tennenhouse, and J.J. Russell © Humana Press, Totowa, NJ
288 Part V / Malignant Skin Diseases Thickening at the base of an AK, the presence of a cutaneous horn, or failure to respond promptly to proper cryotherapy should suggest the possibility of malignancy.
Evolution of Skin Lesions
See Evolution of Disease Process section, above.
Provoking Factors
Extensive sun exposure obtained during recreation or in outdoor occupations is the major cause. Climates with predominantly warm sunny days, increased proximity to the equator, and exposure at higher altitudes all increase the injury, which is of a cumulative nature. These lesions occur primarily in persons of Celtic heritage with types I and II com- plexions, who sunburn easily.
Self-Medication
Inappropriate self-treatment with topical 5-fluorouracil (5-Fu) obtained from relatives or prescribed by misguided practitioners can alter lesions or hide established malignancies without effectively removing them. Patients will also attempt to treat themselves with var- ious cosmetics and patent medications, but soon discover that this is fruitless.
Supplemental Review From General History
A history of lifetime sun exposure, ease of burning, and regular use of sunscreens and protective clothing should be reviewed.
Dermatologic Physical Exam Primary Lesions
1. Erythematous macules and patches 0.5 to 1 cm across (see Photo 36).
2. Thin plaques 0.5 to 1 cm across with secondary changes (see Photo 37).
Secondary Lesions
1. Adherent white, yellow, or brown scale that is removed with difficulty, and upon removal may leave a depressed bleeding base (see Photos 36–39).
2. A cutaneous horn that is firmly attached and may extend a centimeter or more above the normal skin surface (see Photo 38).
3. Erosions (see Photo 39).
4. Ulcerations (see Photo 39).
An indurated base, cutaneous horn, or the presence of erosions or ulceration should raise the possibility of malignant transformation within an AK. If a lesion of this type is treated without biopsy, it should be followed up within 4 to 6 weeks to be certain there has been a complete response.
Distribution
Microdistribution: Follicular: AKs will occasionally occur at the ostium of a hair fol- licle. Follicular AKs are most often seen on the upper facial area and nose. Because the cellular changes extend down the follicular infundibulum, they usually recur after cryotherapy.
Macrodistribution: AKs are distributed on sun-exposed skin such as the upper face, malar and zygomatic eminences, ears, dorsal forearms, and the V area of the upper chest (see Fig. 8).
Configuration
Configuration is grouped.
Indicated Supporting Diagnostic Data Biopsy
The vast majority of AKs can be diagnosed and treated based on clinical examination.
When there is a question about intervening malignancy, a punch biopsy should distinguish them.
Figure 8: Macrodistribution of actinic keratosis.
290 Part V / Malignant Skin Diseases
Therapy Cryosurgery
Light applications of liquid nitrogen (LN2) sufficient to produce a 0.5- to 1-mm rim of freeze at the perimeter of the base of the AK are usually satisfactory for total removal.
The advantage of this technique is the absence of scarring. Persons with olive complex- ions must be warned about the possibility of posttreatment hyper- or hypopigmentation.
During the sunny season, warn patients about sun exposure and the use of a sunscreen with makeup to prevent posttreatment darkening, and for future prevention. Cryosurgery is the technique of choice in patients with a small number of lesions or in patients who cannot comply with, or who refuse, topical therapy. Patients should be warned to return if any lesion fails to resolve within 4 to 6 weeks.
Topical Chemotherapy
The advantage of topical chemotherapy is the ability to destroy actinic damage that is otherwise invisible and would be missed with cryotherapy. Patients with large num- bers of keratoses or a great deal of latent injury, who are reliable and will follow through, are ideal candidates. Topical chemotherapy should be started only after the intended treatment sites have been examined for overtly malignant lesions. This therapy can remove the surface signs of an established cancer while it continues to spread beneath the epidermal surface.
5-fluorouracil: 5-FU selectively seeks out and destroys AKs with little or no effect on the adjacent normal skin. This medication is available as a 0.5% cream with time-releasing microsponges incorporated into the vehicle. It is also marketed as a 1% water-washable cream and as 2% and 5% solutions in propylene glycol. All of the products work in a sim- ilar fashion and have excellent efficacy. The 0.5% cream has the advantage of a single daily application, which improves patient compliance. Patients are instructed to apply the agent to the affected area in a thin layer morning and evening or once daily, depending on the preparation chosen. Careful instructions are needed or the reaction may be very dis- concerting to the patient. Within 5 to 6 days, selected areas of damage and visible ker- atoses will become red, itchy, angry, and irritable. Different patients show different tolerance, and fair-skinned persons seem more reactive. Lesions should be treated until they are inflamed and some of the thinner lesions are coming off. Some lesions may erode and bleed, and patients will need reassurance that this is not a complication. After this point is reached, the treatment is stopped and patients are switched to a low-potency steroid preparation such as topical 0.05% desonide in a soothing lubricating cream base.
This product should be used morning and evening until the redness and irritation has resolved; then it should be discontinued. Follow patients up 6 weeks from the time the 5-FU is stopped. At that time, there are usually scattered thick lesions that have not responded, and these are removed with LN2. During 5-FU treatment, patients should be warned to minimize solar exposure. Significant sun can rapidly accelerate the reaction, and although no permanent injury will result, the effect is frightening and uncomfortable.
A second method of using 5-FU is the “treat through” technique. The drug is contin- ued until the reaction ceases as the AKs are eliminated. Few patients will put up with this duration of irritation, and occasional patients who show nonspecific irritation to 5-FU would not fare well with this technique.
A third method is to use 5-FU and a topical steroid together over a longer period of time. The intent is to reduce irritation and increase compliance. Although reported effec- tive, there is no substantial body of evidence to show that this method has equivalent efficacy.
Diclofenac sodium: This medication is prepared as a 3% gel and is applied twice daily to the affected sun-damaged areas morning and evening. Treatment is recommended for 60 to 90 days, and patients should then have a follow up visit at 6 weeks to freeze any lesions that have not responded. During therapy patients should be warned to minimize sun exposure. This medication is a safe alternative for patients allergic to 5-FU. Head-to- head comparisons with long-term follow-up between the two agents has not been reported.
The prolonged treatment course raises questions regarding patient compliance. Despite claims to the contrary, patients do experience erythema and irritation with diclofenac sodium similar to that seen with 5-FU.
Imiquimod: Imiquimod cream 5%, an immune modulator that has been available for several years for treatment of genital and perianal warts, is also approved for the treatment of actinic keratosis. Like topical 5-FU, it selectivley destroys malignant keratinocytes but leaves normal ones alone. It is applied twice weekly for a period of 16 weeks.
Applications are done at bedtime and left on for 8 hours. Efficacy appears excellent, with 75% or greater reduction of lesions. Drawbacks to this treatment are the prolonged treat- ment time, which would diminish compliance, and the current cost, which is five or six times the cost of other products.
Curettage and Electrodesiccation
Removal by this technique should be undertaken only with the rare lesions that fail to respond to topical or cryotherapy. Although effective, this method of destruction leaves superficial scarring, which is seldom justified. The patient should be forewarned.
Prevention
Solar avoidance and covering up with adequate clothing prevents these premalignant lesions. In female patients, the daily use of makeup that contains or is used over a sun- screen provides substantial protection from keratosis and from the chronic aging effects of the sun. High SPF sunscreen (30 or greater), (preferably containing Parsol), used on a daily basis has been shown to substantially reduce their occurrence.
Conditions That May Simulate Actinic Keratosis Seborrheic Keratosis (SKs)
Pigmented AKs can appear quite similar to early SKs. Actinic lesions are thin and do not show a defined edge or the “stuck-on” appearance of the seborrheic type. In addition, AKs show telangectasia and an adherent scale that often leaves bleeding points when removed.
Solar Lentigo
Pigmented AKs can also be confused with solar lentigines. The latter lesion is usually macular with normal skin markings, whereas the actinic lesion has a scale, and the surface markings are lost.
292 Part V / Malignant Skin Diseases
Discoid Lupus Erythematosus (DLE)
Large AKs can be confused with plaques of DLE because of the telangectasia, adher- ent white scale, and solar distribution. AKs have a more adherent scale, are usually grouped, and do not show the scarring seen with DLE. The scale of DLE, when removed, shows “carpet-tacking” (see Chapter 19).
Squamous Cell Carcinoma
Differentiation from this malignant tumor is discussed in the chapter on squamous cell carcinoma.
ANSWERS TO CLINICAL APPLICATION QUESTIONS
History ReviewA 65-year-old white man is seen at your office for multiple scaling lesions over his face, ears, neck, and the V of the chest. These have developed gradually over several years.
He is an outdoor sportsman. He is concerned about the character and potential of these lesions, and would like to have them removed because they are itchy and irritable.
Physical examination of the involved regions reveals multiple actinic keratoses. Careful examination reveals no lesions that appear overtly malignant.
1. What are the primary lesions that you would expect to find in actinic keratoses?
Answer: Erythematous macules, patches, and thin plaques 5 to 10 mm in size.
2. What are the secondary lesions that you would expect to find in actinic keratoses?
Answer:
a. Adherent white, yellow, or brown scale.
b. Erosions.
c. Ulcerations.
3. What should you tell the patient about actinic keratoses?
Answer: Actinic keratoses are the result of chronic sun exposure and are precan- cerous lesions. Over a period of time, some of them may change into skin cancers.
Removal is recommended because of their malignant potential.
4. How should you treat actinic keratoses in this patient?
Answer: This patient may be treated with topical chemotherapy. Because he has large numbers of lesions, this approach is cost-effective. Cryosurgery is appropri- ate for patients with a small number of actinic keratoses, for patients who cannot comply with a topical chemotherapy regimen, or for patients who simply refuse topical chemotherapy. Cryosurgery is also indicated for the removal of any lesions that do not respond to topical chemotherapy. Topical agents are of marginal value for thick actinic keratoses on the dorsum of the hands and forearms. Cryotherapy is more cost-effective in these locations.
