We previously showed that YAP was up-regulated in cSCC tissues and cell lines compared to normal controls, and its expression had an increasing trend from normal skin → precancerous lesions of actinic keratosis (AK) → carcinoma in situ (Bowen’s Disease) → well-differentiated cSCC → moderately and poorly differentiated cSCC12. This evidence concerns the gene YAP1 and actinic keratosis.