Additional file 1: Figs. S3 and S4 and Tables S2 and S3 show no statistically significant differences in the expression of GSTT1 and UCKL1 in grade I, II, III, and IV inverted papilloma (P > 0.05), suggesting that the expression of GSTT1 and UCKL1 may not be related to the deterioration of SNIP-SCC. Here, UCKL1 is linked to inverted papilloma.