These findings might advance understanding of the pathogenesis behind the development of recurrence in microsurgically resected SIP by focusing on so far neglected alterations of cell-matrix connections at the epithelial-stromal interface in SIP, and might hint at CK14 representing a possible novel biomarker for individual risk assessment in microsurgically resected SIP.

Objective: It was the aim of this study to assess the expression of selected cell cycle regulation genes in urothelial and sinonasal inverted papillomas (IP). Methods: Archived surgically resected specimens from 18 urothelial and 19 sinonasal IP were studied immunohistochemically for p16, p53, cyclin D1 and Ki67. Staining results were semiquantified and compared between IP and adjacent control mucosa (CM). Results: p53 expression did not differ between sinonasal and urothelial IP. Although there was a trend of higher p53 expression in IP compared with the adjacent CM in sinonasal and urothelial specimens, this trend failed to be statistically significant. p16 expression was significantly higher in urothelial IP and CM in comparison with their sinonasal counterparts, but did not differ significantly between IP and its adjacent CM either in urothelial or sinonasal specimens. There were no significant differences in the mean scores for cyclin D1 or Ki67. Conclusion: The changes in p53 expression seen in both types of IP compared with adjacent CM suggest that sinonasal and urothelial IP may share some common ground in terms of their evolution. Although p16 appears not to be directly involved in the development of sinonasal or urothelial IP, the differing recurrence patterns of sinonasal versus urothelial IP may be attributable in part to different p16 expression.

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