Actinic keratosis (AK), also known in layman terms as sunspot, is a pre-cancerous skin condition that appears as a dry, scaly sometimes hyperkeratotic lesion as a result of prolonged and repeated sun exposure. The typical AK lesion is a dry, scaly, skin-coloured, reddish-brown or yellowish-black lesion. The onset of AK is subtle and therefore often passes unnoticed for sometime before diagnosis. AK lesions are usually found on chronically sun-exposed sites of the head and neck and the dorsa of the hands and forearms.

If left untreated, AKs can progress into thickened lesions and subsequently develop into invasive Squamous Cell Carcinoma (SCC). There is an emerging view that AK is an intra-epidermal malignancy and it exists in a continuum with squamous cell carcinoma, the second leading cause of skin cancer deaths in the US, so AK will become SCC when dermal invasion occurs. The American Academy of Dermatolgy reports that 40% of all SCCs begin as AKs.

The majority of patients who have an AK lesion will have multiple lesions and further lesions will become clinically evident in future. Thus an AK patient can face a life time of treatment. AKs are the most common pre-cancerous skin lesions worldwide and the treatment of AKs is the most common dermatologic procedure performed in the out-patient setting.

In the US each year there are 8.2 million office visits for the treatment of AK and AK affects more than 58 million Americans. The annual cost to the US healthcare system for the treatment and management of AK is US$1.2 billion.