Actinic keratoses

• 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.

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