[Beyond actinic keratoses: Field cancerization of the skin]

Lesions occurring in actinic keratoses (AK) form erythematous, squamous, crusty and keratotic papules that appear on skin chronically exposed to the sun due to ultraviolet radiation. They are formed by the proliferation of atypical keratinocytes limited to the epidermis and may progress to squamous cell carcinoma in situ and to cutaneous squamous cell carcinoma (CEC). Although low, the metastatic risk associated with the CEC is not negligible. The concept of field cancerization was introduced in 1953 following studies of neoplastic lesions of the oral mucosa. A cancer field is a normal-looking pre-tumoral zone with subclinical, multifocal anomalies, which may constitute a base for new neoplastic lesions. Such fields are frequently seen in areas of photo-exposed skin and around the edges of AK and CEC. In this event, treatment should not be limited to visible or palpable AK lesions, and if a cancer field is suspected, treatment involving the physical destruction or elimination of atypical keratinocytes from the entire area should be considered. Such an approach may improve the long-term prognosis, reduce treatment costs and ensure optimal cosmetic outcome.