KRT5 and melanoma: Actinic keratoses tend to present CK5/8 positive histochemical panel in epidermis; moreover, some cases present positivity for CK15 and CK19, epidermal stem cell markers, and negativity for CK7.98, 100 Positivity for S100 favors the diagnosis of melanocytic lesions and can be helpful when differentiating actinic keratosis from melanoma.101