Actinic keratoses

Last Updated: 2021-10-18

Author(s): Anzengruber F., Navarini A.

ICD11: EK90.0

  • Dubreuilh 1896.
  • Freudenthal 1926.

Keratinocytic intraepidermal neoplasia, keratosis solaris, keratosis senilis, keratoma senile, AK, Crasse de Vieillard.

Actinic keratoses (AKs) are now often referred to as in-situ squamous cell carcinomas, actinic precancerous lesions or solar keratoses and arise from the proliferation of atypical epidermal keratinocytes. In the course of time, they can develop into spinocellular carcinomas.

  • Actinic keratoses are the most common reason for dermatological presentation in the USA.
  • Men are more frequently affected.
  • The older the patient, the more likely the expression of an actinic keratosis.
  • Prevalence (adulthood): men 15%, women 6%.
  • Prevalence (> 70 y.): men 34%, women 18%. In countries with high UV exposure, the prevalence is correspondingly higher.
  • Patients with high occupational UV exposure (farm workers, roofers, truck drivers!, etc.) can be expected to have a higher prevalence (occupational disease).

  • UV radiation induces mutations (p53, H-ras gene) in keratinocytes, promoting proliferation of atypical cells.
  • In particular, people with chronic sun exposure are prone to actinic keratoses, but (single) sunburns can also increase the risk.
  • Sunscreens reduce the likelihood of the occurrence of actinic keratoses.
  • A light skin type is a predisposing factor.
  • Patients with genetic alterations, such as xeroderma pigmentosum, Bloom syndrome and Rothmund-Thompson syndrome suffer from AKs significantly more often.
  • Human papillomaviruses (HPV) have been detected in actinic keratoses as well as in normal skin, spinocellular carcinomas and basal cell carcinomas. Whether there is a causal relationship between HPV and the occurrence of actinic keratoses is unclear.
  • Immunosuppression increases the risk of suffering from AKs (the risk of an organ transplant is increased approx. 250-fold).

  • Localisation
    • Capillitium (7-fold increased risk in bald men), face, neck, back of hands and forearms.
  • Classical or erythematous type (histologically bowenoid type/atrophic type):
    • Erythematous, rather sharply demarcated, rough, scaly macules, papules and plaques.
  • Keratotic or cornu cutaneum type (histologically hypertrophic type/acantholytic type):
    • Heavily scaling, erythematous, rather sharply demarcated papules and plaques. The horn-like change is called cornu cutaneum.
  • Pigmented type (histologically pigmented type):
    • Actinic keratosis with pigment formation.
  • Lichen planus type (histologically lichenoid type):
    • Difficult to distinguish clinically from erythematous type. Lichenoid appearance.
  • UV-induced changes in the lips are called actinic cheilitis.

  • Clinical manifestation
  • Dermoscopy: i.e. straberry pattern
  • Biopsy especially in infiltrated or painful lesions to exclude invasive carcinoma

Actinically stressed body regions

Orthokeratosis, dyskeratosis, hyperkeratosis, loss of architecture of the epidermis, solar elastosis and keratocyte atopia.

  • Spinocellular carcinoma: In approx. 10% (0.025- 20%) of cases, a spinocellular carcinoma develops from an AK. Conversely, it is assumed that 60% of all spinocellular carcinomas arise from actinic keratoses.
  • Spontaneous regressions are observed in approx. 20-30% (up to 68%) of all AKs, however, 15-53% of regressed, actinic keratoses reappear within one year.
  • In approx. 30% of immunosuppressed patients, an SCC develops.

Apply adequate sun protection, through behaviour (do not stay in the sun between 11:00 and 15:00), textile (UV clothes, hat) and topical (sun cream) protection.

For single lesions:

  • Cryotherapy
    • 2x 5-15 seconds until lesion is frozen through, 1mm border around lesion should also turn white, and a thin frozen platelet should be palpable on palpation. Allow to thaw spontaneously. Success rate is strongly related to application time (39% healing at 5 seconds, 83% at 20 seconds)
      • Hypertrophic AKs and AKs on the back of the hand are persistent and require long and frequent cryotherapy. CAVE: Change pigmentation post-cryotherapy.
  • 5-Fluorouracil ointment 1-2x daily for 3-6 weeks has the best evidence
  • Imiquimod 5% or 3.5% cream
    • 5% cream: 3x/week for 16 weeks, there should be superficial erosion.
    • For large-area use, the use of the 3.5% cream is recommended.
  • Photodynamic therapy (see below)
  • Diclofenac -gel 3% 2x tgl. for 3 months, then control examination.


Photodynamic therapy

  • 14% more successful than cryotherapy (measured after 3 months).
  • Cosmetically more beautiful than cryotherapy or 5- FU.
  • In case of field cancerisation (large area infestation of actinic keratoses), the use of PDT is useful.

1. Conventional PDT:

  • Radiation with red light by PDT devices.

2. Daylight PDT:

  • After exposure to the photosensitiser, the patient should be outdoors for 2 hours (even on cloudy days)
  • Advantages of daylight PDT: ↓ Painfulness, larger areas of skin can be treated, ↓ Cost.
  • Disadvantages of daylight PDT: poorer controllability.
  • To date, randomised studies show no significant difference between daylight PDT with conventional PDT with regard to effectiveness.
  • Advserse reactions with both forms: Pain and change in pigmentation possible.


Surgical interventions

  • Excision, curettage and dermabrasion: only 3rd choice therapies.




Field diameter (cm2)

Fractionation (cGy)

Total dose

Interval between irradiations (days)

















Chemical peeling

  • Trichloroacetic acid 35%- 50% alone or 35% in combination with other substances (Jessner's solution).
  • Reduction of AKs (depending on substance and concentration) by approx. 84%.
  • Recurrence rates: 25-30% after 1 year.



  • CO2 laser or Erbium-YAG also applicable for field cancerisation
  • Complete remission: 90- 91%
  • Recurrence rates: 10-15% after 3-6 months.


Avoid common mistakes:

  • Inform patient about sometimes pronounced side effects.
  • Inform patient about the importance of UV protection.

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