HMGB1 and seborrheic keratosis: Expression of HMGB1 in the epithelial nuclei of highly malignant squamous cell carcinoma was significantly lower than in normal skin and in benign seborrheic keratosis (P = 0.003), but there was no significant difference between seborrheic keratosis, precancerous lesions, basal cell carcinoma and normal skin (Figure 1k).