Crossroads between actinic keratosis and squamous cell carcinoma, and novel pharmacological issues.

Actinic keratoses (AKs) and their derived squamous cell carcinomas are distinctive lesions forming a continuum in a multi-step carcinogenesis process. They are typically found on chronically sun exposed skin. AKs merit to be recognized as such and to be distinguished from squamous cell carcinomas both conceptually and for therapeutic implications. The histological differences between these lesions are well defined and should not be blurred. A brief review is presented about the biological features responsible for AKs and the clinicopathologically distinctive aspects of these lesions. In addition, recent findings are presented about pharmacotherapy using anti-epidermal growth factor receptors, imidazoquinolines, diclofenac-hyaluronan, and methyl aminolevulinate photodynamic therapy.