Actinic keratosis (AK or AKs; Greek: “aktis” ray and “keras” horn; synonyms: actinic precancerosis; keratosis actinis; keratosis solaris; senile keratosis; solar keratosis; sun-induced skin changes; ICD-10-GM L57.0: actinic keratosis) is chronic damage to the keratinized epidermis caused by long-term intense exposure to sunlight (actinic = caused by rays).
The skin damage progresses only slowly, but after years it can lead to squamous cell carcinoma (PEK) of the skin. Actinic keratosis is therefore considered a facultative precancerous condition (risk of degeneration is less than 30%).
The following four subtypes of actinic keratosis can be distinguished:
- Erythematous type
- Keratotic type
- Pigmented type
- Lichen planus type
Actinic keratoses as in situ carcinomas belong to the non-melanoma skin cancer (NMSC).
Actinic keratoses (AK) may progress to invasive squamous cell carcinoma (SCC) after a prolonged latency period.
Actinic keratoses as in situ carcinomas, spinocellular carcinoma and basal cell carcinoma (BCC; basal cell carcinoma) are increasingly also called keratinocyte carcinomas (KC).
Sex Ratio: Males are slightly more commonly affected than females. Frequency peak: The disease occurs predominantly in older age. Increasingly, however, younger people are also affected. The prevalence (disease incidence) is 2.7% of the population. The age-related prevalences for 20-, 30- and 60-year-old patients in Australia are 7%, 27% and 74%, respectively, showing early onset as well as an age-related increase. Fair-skinned people (skin type I/II according to Fitzpatrick) and people with blue eyes are frequently affected. In regions with high UV exposure the prevalence is higher. In Australia, for example, almost half of the men and every third woman in the age group of 30 to 70 years have actinic keratosis.
Course and prognosis: Actinic keratosis may resolve spontaneously (on its own). As a rule, the disease persists for years. In most cases, the course is benign, especially if therapy is given in time.
Actinic keratosis can be recurrent (recurring). After laser therapy, the recurrence rate is 10%.
Since actinic keratosis is a precancerous condition (precancer; KIN (keratinocytic intraepidermal neoplasia)) of squamous cell carcinoma (PEK) of the skin, regular dermatologic follow-up is required. The risk of progression is reported to be up to 16% per year. In up to 10% of cases, actinic keratosis develops into squamous cell carcinoma of the skin within 10 years (synonyms: cutaneous squamous cell carcinoma (SCC); spinalioma; spinocellular carcinoma; spiny cell carcinoma).