Actinic keratoses (AKs) are considered precancerous lesions and present as rough, scaly macules or patches arising on chronically sun-exposed skin. This is a very common condition in individuals with lighter skin colors and is virtually unseen in people with darker skin colors. AKs are commonly seen on sun-exposed skin of the face, ears, scalp (areas of hair loss), neck, upper chest, forearms, dorsal hands, shins, and, less commonly, the eyelids and periocular region. These flat, scaly papules are of varying sizes and usually begin as "rough" localized skin lesions that the patient feels but are difficult to see. They are usually asymptomatic but may be tender.

The frequency of AKs increases with age and cumulative lifetime sun exposure. They are also more common in individuals who are immunosuppressed (especially after solid organ transplantation) and in males. They may resolve with protection from ultraviolet (UV) light. Some medications (ie, capecitabine, sorafenib) may induce inflammation of existing AKs.

Patients with AKs are at higher risk for developing nonmelanoma skin cancer. AKs have the potential to evolve into squamous cell carcinoma (SCC). It is estimated that the likelihood that a given AK will evolve into an invasive SCC is approximately 0.075%-0.096% per lesion.

The term "field cancerization" is used to describe areas of skin at risk for both AK and SCC. Clinically, this manifests as numerous AKs and squamous cell carcinoma in situ (SCCis) with or without invasive SCCs in a field of chronically sun-damaged skin. Risk factors include male sex, lighter skin color, older age, underlying immunosuppression, and the degree of prior exposure to UV light.