HMGB1 and seborrheic keratosis: However, HMGB1 expression in the intracellular space in highly malignant squamous cell carcinoma was lower than in seborrheic keratosis, whereas epithelial nuclear expression of p65, which indicative of NF-κB activation as well as inflammation responses, was higher in squamous cell carcinoma than in all other cell types (P <0.01).