Actinic Keratosis 

Updated: Jan 23, 2020
Author: James M Spencer, MD; Chief Editor: William D James, MD 

Overview

Practice Essentials

Actinic keratosis (AK) is a UV light–induced lesion of the skin that may progress to invasive squamous cell carcinoma. It is by far the most common lesion with malignant potential to arise on the skin. See the image below.

Actinic keratosis. Courtesy of Hon Pak, MD. Actinic keratosis. Courtesy of Hon Pak, MD.

See Nonmelanoma Skin Cancers You Need to Know and Can You Recognize Benign Skin Lesions From Cancerous Ones?, Critical Images slideshows, to help correctly identify various lesions.

Signs and symptoms

Actinic keratoses develop as follows:

  • The lesions begin as small, rough spots that are easier felt than seen and that have what is often described as a sandpaperlike texture[1]

  • With time, the lesions enlarge, usually becoming red and scaly

  • Most lesions are only 3-10 mm, but they may enlarge to several centimeters in size[1, 2, 3]

The typical patient with actinic keratoses is an elderly, fair-skinned, sun-sensitive person.[4] The lesions arise in areas of long-term sun exposure, including the face, ears, and, in men, bald scalp, as well as in the dorsal forearms and hands.[5, 6]

Patients may develop multiple lesions within a single anatomic area, to the extent that the lesions collide and produce confluent actinic keratosis over a relatively large area. The following variants can occur[7] :

  • Brown (pigmented actinic keratosis)

  • Atrophic

  • Bowenoid

  • Lichen planus–like

  • Exaggerated hyperkeratosis - Produces a hornlike projection, known as a cutaneous horn, above the skin surface

The image below is a typical depiction of actinic keratosis.

Erythematous, scaly lesions on the temple area, ty Erythematous, scaly lesions on the temple area, typical of actinic keratosis.

See Clinical Presentation for more detail.

Diagnosis

Histology

A skin biopsy is indicated to confirm the diagnosis and to rule out invasive squamous cell carcinoma for suspicious or more advanced lesions (ie, those with more pronounced hyperkeratosis, increased erythema, or induration or nodularity).[8, 9] A biopsy is also indicated for recurrent lesions or those that are unresponsive to therapy.

Actinic keratosis is characterized by dysplasia and architectural disorder of the epidermis, as follows[1] :

  • Abnormal keratinocytes of the basal layer that are variable in size and shape

  • Altered cellular polarity

  • Nuclear atypia

  • Hyperkeratosis and parakeratosis of the epidermis

  • Irregular acanthosis may be present

In general, hair follicles, sebaceous glands, and apocrine and eccrine ducts are not involved.[1]

Fluorescence

Fluorescence with the use of a photosensitizing drug (methyl ester of 5-aminolevulinic acid [ALA], a precursor of protoporphyrin) commonly used during photodynamic therapy (PDT) has been described as a diagnostic tool for actinic keratosis.[10] Areas of involvement, including occult areas of abnormal skin, emit a pink fluorescence with a Wood lamp or photodynamic therapy lamp.[10]

See Workup for more detail.

Management

Treatment consists of the following categories:

  • Medical therapy - including pharmacologic treatment and PDT

  • Surgical destruction of the lesion

Pharmacologic treatment

Medications approved by the US Food and Drug Administration (FDA) for the treatment of actinic keratosis include the following[11, 12, 13] :

  • Topical 5-fluorouracil (5-FU)

  • Imiquimod cream

  • Ingenol mebutate gel

  • Topical diclofenac gel

Photodynamic therapy

PDT uses a light-sensitizing compound that preferentially accumulates in actinic keratosis cells, where it can be activated by the appropriate wavelength of light. Delta-aminolevulinic acid is a component of the heme biosynthetic pathway that accumulates preferentially in dysplastic cells. Once inside these cells, it is enzymatically converted to protoporphyrin IX, a potent photosensitizer. With exposure to light of an appropriate wavelength, oxygen free radicals are generated and cell death results.[14]

Surgery

Types of surgery used in the eradication of actinic keratoses include the following[15, 16, 17] :

  • Cryosurgery

  • Curettage, shave excision, and conventional excision - For lesions suggestive of invasive cancer

  • Cosmetic resurfacing procedures - Including medium and deep chemical peels, dermabrasion, and ablative laser resurfacing

See Treatment and Medication for more detail.

Background

Actinic keratosis (AK) is a UV light–induced lesion of the skin that may progress to invasive squamous cell carcinoma.[18, 19, 20] It is by far the most common lesion with malignant potential to arise on the skin. Actinic keratosis is seen in fair-skinned persons on skin areas that have had long-term sun exposure.[5] In Australia, the country with the highest skin cancer rate in the world, the prevalence of actinic keratosis among adults older than 40 years has been reported to range from 40-60%.[21]

The premalignant nature of actinic keratosis was recognized almost 100 years ago, and the name literally means thickened scaly growth (keratosis) caused by sunlight (actinic). In the United States, actinic keratosis represents the second most frequent reason for patients to visit a dermatologist.[22]

An actinic keratosis may follow 1 of 3 paths; it may regress, it may persist unchanged, or it may progress to invasive squamous cell carcinoma. The actual percentage that progress to invasive squamous cell carcinoma remains unknown, and estimates have varied from as low as 0.1% to as high as 10%.[18, 23]

In 2009, Criscione and colleagues conducted a study examining the progression of actinic keratoses to squamous cell carcinoma and basal cell carcinoma.[24] The study examined 7784 actinic keratoses in a high-risk population and found that nearly 65% of primary squamous cell carcinomas and 36% of primary basal cell carcinomas arise from clinically diagnosed actinic keratoses. Furthermore, risk of progression of actinic keratosis to squamous cell carcinoma was 0.60% at 1 year and 2.57% at 4 years, which is 6-8 times more frequent than has been reported in some prior studies.

Although it is impossible to predict which individual lesion will follow which course, as most patients have many lesions, accessing risk becomes more significant and aids in tailoring treatments. Overall, actinic keratoses can be safely and effectively eradicated, and, therefore, therapy is warranted.

Pathophysiology

Actinic keratoses arise on fair-skinned people in areas of long-term sun exposure, such as the face, ears, bald scalp, forearms, and backs of the hands.[5] However, they may occur on any area that is repeatedly exposed to the sun, such as the back, the chest, and the legs. Long-term UV light exposure is implicated as the cause from both epidemiologic observations and molecular analysis of tumor cells.[5, 19] Actinic keratosis frequency correlates with cumulative UV exposure.[5] Therefore, the frequency of actinic keratosis increases with each decade of life, is greater in residents of sunny countries closer to the equator, and is greater in persons with outdoor occupations.[4, 5] DNA analysis of the cells within actinic keratoses shows characteristic UV-induced mutations in key genes, including TP53 and deletion of the gene coding for p16 tumor suppressor protein.[19, 25, 26]

Over time, actinic keratoses may develop into invasive squamous cell carcinoma; according to one study of almost 7000 patients, among the small percentage of actinic keratoses that progress into squamous cell carcinoma, the length of time for this transformation to occur was approximately 2 years.[27] Development of actinic keratoses may occur as early as the third or fourth decade of life in patients who live in areas of high solar radiation, are fair-skinned, and do not use sunscreen for photoprotection.[5] Usually, patients demonstrate a background of solar-damaged skin with telangiectasias, elastosis, and pigmented lentigines.[1]

In both histologic and molecular parameters, actinic keratoses share features with squamous cell carcinoma.[28] Actinic keratosis is an epidermal lesion characterized by aggregates of atypical, pleomorphic keratinocytes at the basal layer that may extend upwards to involve the granular and cornified layers.[28] The epidermis itself shows an abnormal architecture, with acanthosis, parakeratosis, and dyskeratosis. Cellular atypia is present, and the keratinocytes vary in size and shape; mitotic figures are present.[28] This presentation may resemble Bowen disease or carcinoma in situ, and the distinction between the two is a matter of degree (extent of the lesion) rather than differences in individual cells.[28]

Etiology

Actinic keratoses are induced by UV light. Both epidemiologic observations and molecular biologic characteristics of the tumor cells suggest UV light is sufficient by itself to induce actinic keratosis.[19, 26] Sensitivity to UV light is inherited; actinic keratoses occur more frequently in fair, redheaded, or blonde patients who burn frequently and tan poorly.[5] Increased sun exposure and higher-intensity exposure increase the chance of actinic keratosis development. Immunosuppression following organ transplantation dramatically increases the risk of developing actinic keratoses[29] ; however, actinic keratoses do not occur without sun exposure.

Additional studies have shown an association between cutaneous human papillomavirus and actinic keratosis.[30, 31, 32] The role of human papillomavirus in skin tumorigenesis was discovered the 1950s, and the group of known human papillomavirus types associated with skin tumorigenesis has been classified as beta-papillomavirus.[31] Beta-papillomavirus DNA has been identified in healthy skin and in squamous cell carcinoma, basal cell carcinoma, and actinic keratosis. A 2007 study suggests that only a small association exists between beta-papillomavirus and actinic keratosis; however, when evaluated in combination with other risk factors including age, sun damage, and ski

Epidemiology

United States

Actinic keratosis occurs primarily in whites, the frequency of which correlates with cumulative UV exposure.[5] Therefore, frequency increases with age, proximity to the equator, and outdoor occupation. Actinic keratoses are seen more in men than in women and have also been correlated with a high-fat diet.[4, 33] Overall, the rate in the United States is estimated to range from 11-26%.[21]

International

The prevalence is highest in Australia, where a light-skinned population is common and outdoor sports are very popular activities.[34] Overall, actinic keratosis is estimated to be present in 40-60% of the Australian population older than 40 years.[21]

Race

The prevalence of actinic keratosis is much higher in individuals with fair skin and blue eyes and is lower in individuals with darker skin types.[4] Actinic keratosis is relatively nonexistent in black skin.[35] Patients with actinic keratoses tend to have Fitzpatrick type I or II skin, which burns and does not tan.[5] The prevalence is reduced precipitously in persons with Fitzpatrick types III, IV, and V skin and is nonexistent in those with Fitzpatrick type VI skin.[35] Although the incidence of cutaneous malignancies in darker-skinned individuals is much lower than in white persons, UV exposure may still play a role in the etiology of squamous and basal cell carcinoma; screening and sun safety education should still be promoted because cutaneous malignancies in darker-skinned individuals can be very aggressive.[35]

Sex

The prevalence of actinic keratosis is higher in men than in women.[5] This is theorized to result from a greater likelihood that men have an outdoor occupation and thus have greater cumulative UV exposure.[4]

Age

One of the most important determinants of actinic keratosis risk is age, particularly when evaluated with other strong predictors, including cumulative sun exposure, place of birth, occupation, and skin type.[4, 5] Actinic keratoses can occur in patients aged 20-30 years, but they are more common in patients aged 50 years and older.[5]

Prognosis

The prognosis for actinic keratosis is good. With continuing surveillance and treatment, these lesions can be managed individually. Lesions begin as barely perceivable rough spots of skin, better felt than seen.[1, 10] Early lesions feel like sandpaper; later lesions become erythematous, scaly plaques that may enlarge to several centimeters.[1, 5] Lesions may remain unchanged for years, may spontaneously regress, or may progress to invasive squamous cell carcinoma.[18, 23]

Most actinic keratoses do not progress to invasive squamous cell carcinoma; however, most invasive squamous cell carcinomas have evidence of a preexisting actinic keratosis.[5, 23] Invasive squamous cell carcinoma may produce significant morbidity by direct extension into facial structures. In less than 10% of cases, invasive squamous cell carcinoma may metastasize, with a low 5-year survival rate.[36, 37]  The opportunity for them to develop into invasive squamous cell carcinomas can be prevented by aggressive therapy and sun protection. However, the prognosis in a person with long-term exposure is more guarded because of the multitude of their lesions.

Patients with extensive involvement unresponsive to cryosurgery and topical therapy may benefit from skin resurfacing by dermabrasion,[17] chemical peeling, or laser resurfacing.[16]

Patient Education

Encourage patients to wear sunscreens, to limit sun exposure, and to adjust their hobby or profession to decrease sun exposure. For patient education resources, see the Skin Conditions & Beauty Center. Additionally, see the patient education article Skin Cancer.

 

Presentation

History

Actinic keratoses are seen almost exclusively in whites, especially those with skin phototypes I and II.[4] The incidence increases with each decade of life, and men have a slightly increased frequency of actinic keratosis.[4, 21] Actinic keratosis is correlated with long-term UV exposure, such as occurs in persons with outdoor occupations.[4]

Patient who are immunosuppressed following organ transplantation are at markedly increased risk of developing actinic keratoses.[29] The lesions still arise in areas of long-term exposure,[6, 27, 38] and they are thought to be actinically induced.

Physical Examination

The typical patient with actinic keratoses is an elderly, fair-skinned, sun-sensitive person.[4] The lesions arise in areas of long-term sun exposure, including the face, ears, bald scalp in men, and the dorsal forearms and hands.[5, 6] Actinic keratoses begin as small rough spots that are easier felt than seen, often described as being similar to rubbing sandpaper.[1] With time, the lesions enlarge, usually becoming red and scaly; most are only 3-10 mm, but they may enlarge to several centimeters.[1, 2, 3] Note the images below.

Actinic keratosis. Courtesy of Hon Pak, MD. Actinic keratosis. Courtesy of Hon Pak, MD.
Erythematous, scaly lesions on the temple area, ty Erythematous, scaly lesions on the temple area, typical of actinic keratosis.

Patients may develop multiple lesions within a single anatomic area, to the extent that the lesions collide and produce confluent actinic keratosis over a relatively large area. Variants may be brown (pigmented actinic keratosis), atrophic, bowenoid, lichen planus–like, or have exaggerated hyperkeratosis, producing a hornlike projection above the skin surface known as a cutaneous horn.[7]

Complications

Lesions may progress into invasive squamous cell carcinomas. A biopsy should be performed on nodular, indurated, or unresponsive lesions.[9]

 

DDx

Diagnostic Considerations

Also consider the following:

  • Discoid lupus erythematosus - Demonstrates dyspigmentation, dilated follicles, and atrophy
  • Seborrheic keratosis - Greasy, brown crusts; sharply demarcated borders; nonerythematous base; may occur in nonexposed areas
  • Bowen disease - A larger plaque with a sharp outline
  • Invasive squamous cell and basal cell carcinomas - Indurated nodular lesions, more rapid growth, eroded or ulcerated surface [8, 9]

Differential Diagnoses

 

Workup

Laboratory Studies

Blood work is not indicated.

Procedures

A skin biopsy is indicated to confirm the diagnosis and to rule out invasive squamous cell carcinoma for suspicious or more advanced lesions (ie, those with more pronounced hyperkeratosis, increased erythema, induration or nodularity).[8, 9] A biopsy is also indicated for recurrent lesions or those that are unresponsive to therapy.

Fluorescence with the use of a photosensitizing drug (methyl ester of 5-aminolevulinic acid [ALA], a precursor of protoporphyrin) commonly used during photodynamic therapy (PDT) has been described as a diagnostic tool for actinic keratosis.[10] Areas of involvement, including occult areas of abnormal skin, emit a pink fluorescence with a Wood lamp or photodynamic therapy lamp.[10]

Histologic Findings

Actinic keratosis is characterized by dysplasia and architectural disorder of the epidermis.[1] Keratinocytes of the basal layer are abnormal and are variable in size and shape; cellular polarity is altered, and nuclear atypia is seen.[1] These alterations may extend upward to the granular layer, which may be thinned. Overall, the epidermis exhibits hyperkeratosis and parakeratosis, and irregular acanthosis may be present.[1] In general, hair follicles, sebaceous glands, and apocrine and eccrine ducts are not involved.[1]

 

Treatment

Medical Care

Actinic keratoses may remain unchanged, spontaneously resolve, or progress to invasive squamous cell carcinoma.[1] The fate of any one actinic keratosis is impossible to predict. Although the risk of progression of any one actinic keratosis to invasive squamous cell carcinoma is small (at most approximately 10%),[18] a patient may have many lesions, and thus the risk of progression becomes significant. Additionally, actinic keratoses can be clinically indistinguishable from more serious cutaneous malignancies, including squamous cell carcinoma and lentigo maligna.[39, 40] Therapy is generally well tolerated and simple; therefore, treatment of all actinic keratoses is warranted.

The appropriate treatment is generally chosen based on the number of lesions present and the efficacy of the treatment.[41] Additional variables to consider include persistence of the lesion(s), age of the patient, history of skin cancer, and tolerability of the treatment modality.[18] Treatment consists of 2 broad categories: surgical destruction of the lesion and medical therapy. Medical management begins with educating the patient to limit sun exposure. Patients should be cautioned to avoid sun exposure from 10:00 am to 3:00 pm as much as possible. They also must wear adequate sunscreens and protective clothing daily.[42]

Medical therapy has the advantage of being able to treat large areas with many lesions. The disadvantages of medical therapies include lengthy courses of treatment with irritation and discomfort. The US Food and Drug Administration (FDA) has approved five medications for the treatment of actinic keratoses. These are topical 5-fluorouracil (5-FU), 5% and 3.75% imiquimod cream, topical diclofenac gel, ingenol mebutate, and PDT with topical delta-aminolevulinic acid.[11, 12, 13]

5-Fluorouracil

The most experience in topical therapy for actinic keratoses is with 5-FU, known to inhibit thymidylate synthetase and cause cell death in actively proliferating cells.[43] Several formulations are available, including a 5% cream or solution, a 2% solution, a 1% cream or solution, and, most recently, a micronized 0.5% cream.[11] Although not well studied, efficacy among the various formulations does not seem to differ significantly.[44, 45]

The most popular formulation is the 5% cream, which is applied twice daily for 1 month. During the treatment phase, the lesions become increasingly erythematous and cause discomfort; small subclinical lesions become visible. This treatment can be temporarily disfiguring, with erythematous ulcerations and crust formation. However, if the patient completes the treatment, the lesions usually heal within 2 weeks of stopping treatment, the complexion is smooth, and the actinic keratoses are improved.

The 0.5% micronized cream was developed to increase tolerability because inflammation and discomfort can be a limiting factor in the use of topical 5-FU. The 0.5% micronized cream is applied once daily for 1 month.

Usage of the 0.5% micronized cream 1 week prior to cryosurgery has also been shown to produce complete lesion clearance in a higher number of patients compared with cryosurgery alone (32.4% and 15%, respectively).[46] Note the images below.

Actinic keratosis during treatment with topical 5- Actinic keratosis during treatment with topical 5-fluorouracil. Courtesy of Hon Pak, MD.
Actinic keratosis right after treatment with topic Actinic keratosis right after treatment with topical 5-fluorouracil. Courtesy of Hon Pak, MD.

Imiquimod

Imiquimod is a topical medication that up-regulates a variety of cytokines, which, in turn, invoke a nonspecific immune response (interferons, natural killer cells) and a specific immune response (T cells). It is applied 2-3 times a week for up to 4 months, although generally 1 month is sufficient.[47] Reaction to the drug is idiosyncratic, with some patients barely reacting and others developing marked inflammation. Subclinical lesions previously not appreciated may become inflamed during therapy. In patients with a brisk inflammatory response, dosing is reduced to twice or even once a week, with preservation of therapeutic efficacy but increased tolerability.

Two new formulations of imiquimod (2.5% and 3.75%) were studied and found to be efficacious in clearing actinic keratoses (25% and 34% clearance, respectively), with a more intuitive daily dosing schedule. Although not as efficacious as 5% imiquimod, the new formulations cause less irritation, promoting better compliance.[48] Experimental evidence suggests patients may develop T-cell memory after treatment with this drug and thus may be less likely to develop new actinic keratoses in the future. Imiquimod 5% cream has also been shown to be safe and effective in transplantation patients.[49, 50]

Ingenol mebutate topical

Ingenol mebutate gel (Picato) was approved by the FDA for actinic keratosis in January 2012 as a 2-3 day course of therapy. The dosage for actinic keratosis differs depending on the application site. The 0.015% gel is used for application to the face or scalp for 3 consecutive days, whereas the 0.05% gel is used for application to the trunk or extremities for 2 consecutive days.

Four multicenter, randomized, double-blind studies showed that ingenol mebutate gel applied topically for 2-3 days is effective for field treatment of actinic keratoses. The studies reported adverse effects that were generally mild to moderate in intensity and resolved without sequelae.[51] A phase III randomized, double-blind study displayed long-term benefit of ingenol mebutate 0.015% gel for both initial and follow-up therapy.[52] A posthoc analysis of patient-reported outcomes from phase III trials using ingenol mebutate gel for actinic keratosis found that treatment with this gel improved patients’ quality of life and treatment satisfaction, owing to higher degrees of lesion clearance.[53]

Although a precise mechanism of action has not been defined, a dual mechanism of action was described by Rosen et al. This dual mechanism includes (1) rapid lesion necrosis by mitochondrial swelling and membrane disruption and (2) specific neutrophil-mediated, antibody-dependent cellular cytotoxicity by antibodies produced from B cells that bind to antigens on dysplastic epidermal cells.[54]

Follow-up study supports these findings.[55, 56]

Jim On et al investigated the hypothesis that ingenol mebutate gel targets cell death in proliferating keratinocytes versus healthy skin by studying the local skin reaction (LSR) score after two cycles of treatment. The study included 20 participants with actinic keratoses on their face and scalp who applied 0.015% gel once daily for 3 days in two sequential 4-week cycles. The study found that the composite LSR score was significantly lower during the second cycle, thus suggesting that ingenol mebutate gel provides targeted therapy of actinic keratoses over cumulative dosing.[57]

In January 2020 as a precautionary measure, the European Medicines Agency (EMA) suspended the marketing authorization for ingenol mebutate (Picato) and recommended patients stop using the medication.[58] The EMA noted a trial that compared imiquimod and ingenol mebutate and found that skin cancer was more common in areas treated with ingenol mebutate versus imiquimod. The EMA notes that alternative treatments are available. The US Food and Drug Administration is investigating but has not made the recommendation to suspend use.

Topical diclofenac sodium 3% gel

Topical diclofenac sodium 3% gel is a nonsteroidal anti-inflammatory drug approved by the FDA for the treatment of actinic keratosis. Its mechanism of action against actinic keratoses is unknown. It is effective therapy when applied twice a day for 3 months. A shorter course of therapy is dramatically less effective. Its chief advantage is that it produces little-to-no inflammation and thus is very well tolerated. Diclofenac therapy after cryosurgery has also been shown to produce complete lesion clearance in a higher number of patients compared with cryosurgery alone (64% vs 32%, respectively).[59]

Photodynamic therapy

PDT uses a light-sensitizing compound that preferentially accumulates in actinic keratosis cells, where it can be activated by the appropriate wavelength of light. Delta-aminolevulinic acid is a component of the heme biosynthetic pathway that accumulates preferentially in dysplastic cells. Once inside these cells, it is enzymatically converted to protoporphyrin IX, a potent photosensitizer. With exposure to light of an appropriate wavelength, oxygen free radicals are generated and cell death results.[14]

Patients experience pain, similar in scope to the pain resulting from topical 5-FU, in the areas treated. The treated lesions may become erythematous and crusted. One treatment with PDT appears to be as effective as topical 5-FU therapy.[60]

A recent meta-analysis and systematic review assessed the effectiveness of PDT versus cryotherapy and found that PDT had a 14% better chance of complete lesion clearance at 3 months for thin actinic keratoses on the face and scalp compared with cryotherapy.[61]

Immunosuppressed patients may also benefit from PDT in the prevention of nonmelanoma skin cancers.[62]

When used with light sources that have a cosmetic benefit by themselves, such as the pulsed dye laser or intense pulsed light devices, a cosmetic benefit may be seen from the use of topical PDT beyond that of actinic keratosis eradication. Compared with other destructive therapeutic options such as cryotherapy, PDT may offer better cosmetic results and higher patient preference.[62, 63]

An unknown parameter in the use of topical PDT is the optimal incubation time following application of the topical aminolevulinic acid before light exposure. A second unknown parameter is the optimal light source to use for this treatment. Ongoing studies are addressing these issues.[62, 64]

Another photosensitizing agent approved in the use of PDT is methyl-5-aminolaevulinate (MAL). Comparison studies between ALA and MAL are not currently decisive. A study investigating the clinical efficacy of ALA- versus MAL-PDT in the treatment of actinic keratosis, Bowen disease, nodular basal cell carcinoma, and superficial basal cell carcinoma found that there were no statistically significant differences in their treatment outcomes using either of these agents.[65] However, a randomized, multicenter, observer-blind, placebo-controlled trial comparing the efficacy of BF-200 ALA versus MAL cream in the treatment of actinic keratoses lesions demonstrated that PDT with BF-200 ALA was superior to the MAL cream regarding patient complete clearance of lesions. Six- and 12-month follow-up studies substantiated the efficacy of PDT with BF-200 ALA and the lower recurrence rates of lesions with BF-200 ALA treatment versus MAL treatment.[66, 67] Looking beyond lesion clearance, MAL -PDT was found to be less painful when compared with ALA-PDT in a retrospective monocentric study of 173 patients.[68]

Surgical Care

The goal of surgical therapy is complete eradication of the actinic keratoses, usually by physical destruction, with limited-to-no damage to surrounding healthy tissue. When the diagnosis is unclear and an invasive tumor is possible, biopsy is indicated. However, biopsy generally leaves a scar.

Cryosurgery refers to use of a cryogen to lower the temperature of the skin and produce cell death. The most common cryogen used is liquid nitrogen, with a temperature of -195.8°C. Keratinocytes die when exposed to approximately -40 to -50°C. Other structures in the skin, such as collagen, blood vessels, and nerves, are more resistant to the lethal effects of cold than keratinocytes. Melanocytes are more sensitive than keratinocytes; thus, cryosurgery often leaves white spots. This technique has not been studied in a scientific fashion until 2004, when it was demonstrated to produce an overall clearance rate of 67-88%.[63, 69]

Lesions suggestive of invasive cancer may be treated with curettage, shave excision, or conventional excision, all of which provide a sample for histologic evaluation. These treatments require local anesthesia, produce a wound that requires time to heal, and are likely to scar.

Cosmetic resurfacing procedures, in which the entire epidermis is removed, sometimes with some portion of the dermis, are effective for actinic keratosis eradication. Cosmetic resurfacing procedures include medium and deep chemical peels, dermabrasion, and ablative laser resurfacing.[15, 16, 17] All of these are cosmetic procedures unlikely to be covered by insurance, all carry the risk of scarring and infection, and all require experience and expertise on the part of the dermatologic surgeon. They are highly unlikely to be performed solely for actinic keratosis therapy.

Diet

One study has suggested that a low-fat diet in humans leads to greater resolution of existent actinic keratoses and the development of fewer new ones during the study period.[33]

Activity

Instruct patients to practice sun safety, such as the use of sunscreen and protective clothing, and to limit outdoor activity from 10:00 am to 3:00 pm.[42]

Prevention

The development of these lesions is directly proportional to sun exposure. Actinic keratoses can be reduced or delayed by using sunscreens and reducing sun exposure.[42] Patients should limit recreational exposure, and those who work outdoors should consider making adjustments in their work-related sun exposure. For patients forced to undergo sun exposure, recommend applying a sunscreen of sun protection factor (SPF) 30 or more and wearing protective clothing daily.[42]

Long-Term Monitoring

If the lesions do not respond to topical therapy, they can be treated with cryotherapy with liquid nitrogen spray for 5-20 seconds.[69] Lesions become irritated and ulcerate, and eventually the diseased pathology is sloughed from healthy skin.[69]

A biopsy of more advanced lesions that are indurated should be performed to rule out an invasive carcinoma.[9]

 

Medication

Medication Summary

The goals of pharmacotherapy are to reduce morbidity and to prevent complications.

Antineoplastic Agent, Topical

Class Summary

The drug of choice is topical 5-FU lotion or cream, which inhibits cell growth and proliferation.

Fluorouracil topical (Fluoroplex, Carac, Efudex, Tolak)

Fluorouracil topical is used topically for the management of actinic keratoses. It interferes with DNA synthesis by blocking methylation of deoxyuridylic acid via inhibition of thymidylate synthetase and, subsequently, cell proliferation. For lesions on bald scalp or extremities, longer treatment is often necessary.

Ingenol mebutate topical (Picato)

The precise mechanism by which ingenol mebutate causes cell death in actinic keratosis is unknown, but it may include a dual action of (1) rapid lesion necrosis by mitochondrial swelling and membrane disruption and (2) specific neutrophil-mediated, antibody-dependent cellular cytotoxicity by antibodies produced from B cells that bind to antigens on dysplastic epidermal cells.

The dosage for actinic keratosis differs depending on the application site. The 0.015% gel is used for application to the face or scalp for 3 consecutive days, whereas the 0.05% gel is used for application to the trunk or extremities for 2 consecutive days.

Immunomodulator, Topical

Class Summary

Investigation of imiquimod demonstrates it induces interferons alpha and gamma, TNF-alpha, and interleukin 12, among other cytokines. Studies using 5% cream in mice showed significant induction of interferon alpha at the site of application, occurring as early as 2 hours after treatment. At 4 hours after application, increases in interferon alpha mRNA levels were found, indicating an increase in transcription. Cytokine up-regulation is thought to be activated by imiquimod binding to toll-like receptor VII.

Imiquimod (Aldara 5% cream, Zyclara 3.75% cream)

Imiquimod is an immune response modifier thought to produce a nonspecific anti–actinic keratosis response, interferon, natural killer cells, and a specific immune response (cytotoxic T cells). It is indicated for clinically typical, nonhyperkeratotic, nonhypertrophic actinic keratoses on the face or scalp.

Photosensitizing Agent, Topical

Class Summary

Topical photosensitizing agents are administered in combination with PDT.

Aminolevulinic acid (Levulan Kerastick, Ameluz)

This agent is a porphyrin precursor used in combination with narrow-band, red-light illumination for nonhyperkeratotic, nonpigmented actinic keratoses. When used with PDT, accumulation of photoactive porphyrins produces a photodynamic reaction that results in a cytotoxic process dependent upon the simultaneous presence of oxygen.

PDT with aminolevulinic acid is a 2-stage process involving application of the solution followed by illumination with blue light 14-18 hours later; treatment may be repeated every 8 weeks.

Topical solution 20% is intended for direct application to individual lesions diagnosed as actinic keratosis and not to perilesional skin. Application should involve either scalp or face lesions, but not both simultaneously. Recommended treatment frequency is 1 application and 1 dose of illumination per treatment site per 8-week treatment session. Each Levulan Kerastick should be used for only one patient.

Topical solution 10% is to be applied 1 mm thick to actinic keratosis and to approximately 5 mm of surrounding skin. Application area should not exceed 20 cm2 and 2 g at one time. After covering with a light-blocking occlusive dressing for 3 hours, remove the dressing, wipe off the remaining gel, and follow with red light illumination.

Nonsteroidal Anti-inflammatory Drug, Topical

Diclofenac transdermal gel (3%)

Diclofenac topical is designated chemically as 2-[(2,6-dichlorophenyl) amino] benzeneacetic acid, monosodium salt, with an empirical formula of C14 H10 Cl2 NO2 Na. It is one of a series of phenylacetic acids that has demonstrated anti-inflammatory and analgesic properties in pharmacological studies. It is believed to inhibit the enzyme cyclooxygenase, which is essential in the biosynthesis of prostaglandins. Diclofenac topical can cause hepatotoxicity; hence, liver enzyme levels should be monitored in first 8 weeks of treatment.

It is used topically as a keratolytic agent to treat actinic keratoses.

 

Questions & Answers

Overview

What is the role of fluorescence in the diagnosis of actinic keratosis?

What is actinic keratosis?

What are the signs and symptoms of actinic keratosis?

How are the lesions of actinic keratosis characterized?

What is the role of skin biopsy in the diagnosis of actinic keratosis?

How is actinic keratosis characterized?

What are the treatment options for actinic keratosis?

Which medications are FDA approved for the treatment of actinic keratosis?

What is the role of photodynamic therapy in the treatment of actinic keratosis?

What are the surgical options for eradication of actinic keratosis?

What is actinic keratosis?

What is the pathophysiology of actinic keratosis?

What causes actinic keratosis?

What is the prevalence of actinic keratosis in the US?

What is the global prevalence of actinic keratosis?

What are the racial predilections in prevalence of actinic keratosis?

What is the sexual predilection in prevalence of actinic keratosis?

Which age groups have the highest prevalence of actinic keratosis?

What is the prognosis of actinic keratosis?

What is included in patient education about actinic keratosis?

Presentation

Which clinical history findings are characteristic of actinic keratosis?

Which physical findings are characteristic of actinic keratosis?

What are complications of actinic keratosis?

DDX

Which conditions should be included in the differential diagnosis of actinic keratosis?

What are the differential diagnoses for Actinic Keratosis?

Workup

What is the role of lab tests in the workup of actinic keratosis?

What is the role of skin biopsy in the workup of actinic keratosis?

What is the role of florescence in the workup of actinic keratosis?

Which histologic findings are characteristic of actinic keratosis?

Treatment

What are the treatment options for actinic keratosis?

What is the role of 5-fluorouracil (5-FU) in the treatment of actinic keratosis?

What is the role of imiquimod in the treatment of actinic keratosis?

What is the role of ingenol mebutate gel (Picato) in the treatment of actinic keratosis?

What is the role of topical diclofenac sodium 3% gel in the treatment of actinic keratosis?

What is the role of photodynamic therapy in the treatment of actinic keratosis?

What is the role of surgery in the treatment of actinic keratosis?

What is the role of dietary modification in the treatment of actinic keratosis?

Which activity modifications are used in the treatment of actinic keratosis?

How is actinic keratosis prevented?

What is included in the long-term monitoring of patients with actinic keratosis?

Medications

What are goals of drug treatment for actinic keratosis?

Which medications in the drug class Nonsteroidal Anti-inflammatory Drug, Topical are used in the treatment of Actinic Keratosis?

Which medications in the drug class Photosensitizing Agent, Topical are used in the treatment of Actinic Keratosis?

Which medications in the drug class Immunomodulator, Topical are used in the treatment of Actinic Keratosis?

Which medications in the drug class Antineoplastic Agent, Topical are used in the treatment of Actinic Keratosis?