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Introduction

An actinic keratosis (AK) is a common sun-induced scaly or hyperkeratotic lesion, which has the potential to become malignant. NICE estimates that over 23% of the UK population aged 60 and above have an AK. Although the risk of an AK transforming into a squamous cell carcinoma (SCC) is very low, this risk increases over time and with larger numbers of lesions. The presence of ten AK is associated with a 14% risk of developing an SCC within five years.

Aetiology

  • AK are a consequence of cumulative long-term sun-exposure:
    • lesions are very uncommon under the age of 45 years
    • the incidence increases with age
    • the exceptions are patients with xeroderma pigmentosum and albinism who can develop AK at a very young age
  • Genetic factors play a role and individuals with fair skin, blue eyes and blonde hair are at higher risk, whereas lesions are exceedingly rare in patients of skin types IV–VI
  • Artificial UV radiation such as UVB and PUVA, used to treat psoriasis and a number of other skin conditions, as well as the use of sun beds, increase the risk
  • Men are more affected than women.

Clinical findings

Clinical examination

  • There is often a background of significant sun-damaged skin with pigment irregularity, telangiectasia, erythema and collagenosis (a yellow papularity of the skin)
  • Distribution
    • this reflects the intensity of sun-exposure with the greatest number of lesions occurring on the head, neck, forearms and hands
  • Morphology
    • lesions usually take on a similar appearance
    • seldom exceed more than 1 cm in diameter
    • rough surface scale—usually white, although in patients with skin type I AK are often more easier felt than seen
    • often termed as flat, but some lesions can have significant amounts of scale (hypertrophic or Bowenoid AK).

Dermoscopic features

  • A red pseudonetwork
  • Strawberry-like appearance
  • Structures may not be visible if there is a lot of scale.

AK variants

  • Erythematous (the rough scale is more palpable than visible)
  • Pigmented
  • Hypertrophic/Bowenoid (thick areas of scale)
  • Cutaneous horn: a horny protuberance, the majority are caused by AK or warts but 15% are secondary to an underlying SCC—refer to the related chapter on cutaneous horns
  • Lichenoid (smooth and shiny, mainly occurring in areas of friction)
  • Actinic chelitis (lips).

Management

Who should manage AK?

Given the very large numbers of patients who have AK it is important that the majority should be managed in the community, and preferably by GPs, otherwise consultant and general practitioner with a special interest (GPwSI) clinics will become overburdened, and patients with more serious skin problems will wait longer to be seen by a specialist.

Who should be referred?

  • Refer the following to a GPwSI or consultant dermatologist:
    • diagnostic uncertainty
    • advice on treatment for patients with more widespread/severe actinic damage
  • If the lesion is suspicious of an SCC refer to secondary care as a two-week rule (the majority should be referred to dermatology, although if very suspicious for an SCC consider referral to plastic surgery—check local guidelines). The following could suggest transformation from an AK into an SCC:
    • history—recent growth/pain/bleeding
    • examination
      • an elevated lesion (papule/nodule)—remove any surface scale if present to make a proper assessment of the lesion
      • ulceration
      • induration
      • tenderness
      • surrounding inflammation
    • beware lesions on lips—SCC can be very subtle at this site
  • Other patients that should be referred to a dermatologist are those with actinic damage who are at a much higher risk of developing an SCC:
    • immunosuppressed patients, in particular post-transplant
    • very young patients presenting with AK—consider xeroderma pigmentosum.

Treatment of AK

Step 1: general measures—appropriate for all patients

  • AK are a marker of sun damage and so a thorough skin examination is needed to look for more serious sun-related skin tumours
  • Provide a patient information leaflet on UV protection (and vitamin D) including the need to wear a hat—up to 25% of AK will resolve if patients adhere to advice
  • Provide a patient information leaflet on AK
  • Moisturisers—it can sometimes be difficult to differentiate between early AK and dry scaly areas of normal skin. The use of a moisturiser two to three times a day can be helpful in differentiating between areas of normal and abnormal skin
  • Patient expectation—once patients start to develop AK they will almost certainly develop more. The aim of any treatment is to reduce the total number of AK on the skin at any one time
  • Education—inform patients which skin changes need to be reported. Transformation into an SCC can be suggested by recent growth, discomfort, ulceration/bleeding. Patients also need to report any other skin lesions they are not familiar with
  • Recommend that patients with larger numbers of actinic keratoses take nicotinamide 500 mg BD, a vitamin that has been shown to reduce the number of actinic keratoses and non-melanoma skin cancers.

Step 2: observation

  • Not all patients need treating e.g. patients with smaller numbers of lesions, especially if they have a reduced life expectancy—such patients should be given a choice of whether or not they wish to have their lesions treated.

Step 3: lesion specific treatment i.e. a few lesions or larger numbers that are widely distributed (i.e. dotted around the face, scalp, and hands etc)

  • Treat the individual lesions and not the normal surrounding skin
    • Efudix® cream (5-FU)—apply every night for four weeks. Wash hands thoroughly after application. Leave treated areas uncovered and wash the following morning. Patients should be advised to expect a relatively mild degree of redness and discomfort during the treatment period
    • Actikerall® solution combines 5-FU with salicylic acid and as such it is also suitable for treating moderately thick (hyperkeratotic) AK—it should be used once a day for six to 12 weeks. Actikerall tends to leave a film on the skin, which should be washed/peeled off before the next application
    • cryotherapy—a single freeze-thaw cycle of approximately 10 seconds (avoid the gaiter area of the legs due to risk of leg ulceration).

Step 4: field change

Field change refers to areas of skin that have multiple AK associated with a background of erythema, telangiectasia and other changes seen in sun-damaged skin. These areas are probably more at risk of developing SCC, especially if left untreated and, as such, it is recommended that they should be treated more vigorously. As such, the treatments should be applied to the whole area of field change and not just the individual lesions.

As when treating other patients with actinic keratoses the primary aim of treatment is to reduce the total number of lesions that the patient has at any one time, the fewer lesions a patient has the less risk they have for developing an SCC. Treatment courses will need to be repeated from time to time. Note that all field-based treatments will elicit local skin responses, which are expected as part of the treatment. The length of time a patient has to endure local skin responses varies widely between the treatments referred to below, and this needs to be discussed with the patient to aid them with the decision-making.

  • For smaller areas of field change (e.g. an area the size of a palm or most of the forehead) consider the following treatments, which are listed alphabetically:
    • Actikerall® solution (combines 5-FU with salicylic acid)
      • used once a day for six to 12 weeks. Actikerall tends to leave a film on the skin, which should be washed/peeled off before the next application
    • Aldara® cream (5% imiquimod)
      • use three nights a week e.g. Monday, Wednesday and Friday for four weeks. Apply overnight and wash off the following morning. After four weeks stop the treatment and consider the use of a mild topical steroid e.g. 1% hydrocortisone or Eumovate® cream BD for two to four weeks to help settle down any inflammation. Follow up three months after the treatment was started, repeat the treatment if needed
      • advantages—generally very effective in terms of clearance, and cosmetic appearance once inflammation resolved
      • disadvantages—patients should be warned to expect marked erythema with crusting of the skin. Timing of the treatment is important and is best avoided during holidays and important social occasions. Some patients develop flu-like symptoms during treatment
    • Efudix® cream (5-FU)
      • use once a day for four weeks. Apply thinly in an evening with a gloved finger, alternatively wash the finger after application. The treated area should be washed the following morning. After four weeks stop the treatment and consider the use of a mild topical steroid e.g. 1% hydrocortisone or Eumovate® cream BD for two to four weeks to help settle down any inflammation. Follow up three months after the treatment was started
      • advantages and disadvantages similar to Aldara®, although patients do not develop flu-like symptoms
    • Photodynamic therapy
      • this is provided by some dermatology departments and occasionally GPwSI clinics
      • a single treatment often provides an effective treatment for an area of field change. The skin settles down within a few days of treatment. Cosmetic outcomes are good
  • For larger areas of field change consider the following treatments (listed alphabetically):
    • Solaraze® gel (3% diclofenac in sodium hyaluronate)
      • use twice a day for eight to 12 weeks. Review patient four weeks after treatment has finished to assess response
      • advantages—generally well-tolerated and so can be used on any sized area
      • disadvantages—most dermatologists view Solaraze as a milder treatment, which may not be as effective as some of the other treatments and so is best used where the AK are thin. Once treatment is complete any remaining AK can then be managed with the treatments referred to in step three above
    • Zyclara® cream (3.75% imiquimod cream)
      • apply once daily for two weeks, followed by a two-week treatment-free period, and then a further once daily application for two weeks (i.e. six weeks in total, but only four weeks of treatment)
      • adverse effects less than when using Aldara® cream (5% imiquimod).

Erosive pustular dermatosis of the scalp

  • Is an uncommon condition affecting UV-damaged areas of the scalp in older patients. The risk appears to be increased with the subsequent treatment of actinic keratoses, especially with cryotherapy
  • Clinically there is varying degrees of scarring associated with yellow-brown crusts, pustules, lakes of pus, erosions and ulceration
  • The primary treatment is the use of super-potent topical steroids.

Algorithm 1: AK treatment pathway

PCDS Actinic Keratosis v4

Actinic (solar) keratosis—primary care treatment pathway. Download a PDF of this pathway

Please note the recommendations in the treatment pathway do not take into consideration the cost of treatment and are based on the clinical expertise of the guideline contributors with the products.

Full guideline: Primary Care Dermatology Society. Actinic (Solar) Keratosis primary care treatment pathway. PCDS, 2020. Available from: www.pcds.org.uk/clinical-guidance/actinic-keratosis-syn.-solar-keratosis

Primary Care Dermatology Society, PO Box 789, Rickmansworth, WD3 0NU (Tel—0333 939 0126)
www.pcds.org.uk

First included: June 2013

Last updated: April 2020.