ZEB1 and actinic keratosis: The tumor stage of each tumor was evaluated by assessing the expression of E-cadherin and ZEB-1 by immunoistochemical assay (n = 20) in formalin-fixed paraffin-embedded biopsies of the five stages of the malignant evolution of keratinocytes towards cSCC: normal epidermis, actinic elastosis, advanced actinic keratosis, well-differentiated cSCC, and poorly differentiated SCC (Fig. 7d).