Solar keratosis

Definition/diagnostic criteria Solar keratosis, also known as actinic keratosis (AK), is a common, sun-induced, scaly or hyperkeratotic lesion with the potential to become malignant. It is mainly a consequence of cumulative long-term sun exposure, affecting parts of the body such as the forearms, backs of the hands, face, ears, bald scalp and lower legs​​​​

Epidemiology In the UK, approximately 15-23% of individuals have AK lesions, with a higher prevalence (over 23%) in the population aged 60 and above. Factors that increase the risk include advanced age, male gender, cumulative sun exposure, fair skin, blue eyes, blonde hair, and genetic conditions like xeroderma pigmentosum and albinism​​​​. AKs are very rare in patients with skin types IV-VI.

Diagnosis
Clinical features: Actinic keratoses are usually skin-coloured to pink, can be more easily felt than seen.

• These lesionsmay develop a rough, white surface scale.
• Generally flat but may thicken, and can grow up to 1-2 cm in diameter.
• Not typically painful but may progress to squamous cell carcinoma (SCC), albeit at a low rate​​.
• AKs more commonly look like age spots in people who have skin of colour.

Investigations: The diagnosis is primarily clinical, with the most helpful sign being an irregularly roughened surface texture. Dermatoscopy can assist in differentiating AK from basal cell carcinoma when the lesion is non-keratotic.

It’s important to always consider the possibility of SCC in these cases​​.

Treatment Treatment is considered appropriate due to the potential (albeit low) risk of malignant transformation. In cases of a single AK lesion, a wait-and-see approach might be suggested. However, with multiple lesions or if the lesion is symptomatic (e.g. pain or itchiness), treatment is usually recommended.

Prognosis While the majority of actinic keratoses are harmless and up to 20-30% may regress spontaneously, they carry a small but significant risk of transforming into SCC. Patients with actinic keratoses are at a higher risk for all types of skin cancer compared to those without such lesions. It’s important to monitor these patients for changes in the lesions, such as bleeding, increase in size, change in colour, or development into a lump​​​​.