Actinic Keratosis (AK), also known as Solar Keratosis, is a cutaneous lesion that results from the proliferation of atypical epidermal keratinocytes. They are generally small red, scaly, pre-cancerous bumps and are most commonly detected in adults with fair skin. They feel like sharp little thorns in the skin.

Chronic sun exposure is a significant risk factor for the development of these lesions, which accounts for the usual detection of AKs in frequently sun-exposed areas (eg, balding scalp, face, neck, and forearms). If left untreated, approximately one in ten Actinic Keratosis will develop into a Squamous Cell Carcinoma (SCC).