Inflammation and the pathogenesis of inverted papilloma

Despite existing clinical and histopathological evidence, the role of inflammation in the pathogenesis of inverted papilloma (IP) is not well understood The goal of this study was to describe the inflammatory cell component present in sinonasal papilloma (SP), with the intention of further defining the existence of inflammation in IP and perhaps gaining insight into IP pathophysiology.

Computerized database analysis was performed to identify all patients with SP who underwent surgery at the Cleveland Clinic Foundation between 1995 and 2001. Histopathological features of all SP were reviewed and semiquantitative analysis of the inflammatory cells present was performed. IP was histopathologically graded into four categories by the extent of inflammatory infiltrate and cellular atypia. Statistical analysis of the inflammatory cell component present in the epithelial layer of exophytic papilloma and IP was performed.

SP was classified into three types: cylindrical papilloma (5% [2/41]), exophytic squamous papilloma (34% [14/ 41]), and IP (61% [25/41]). Twenty-eight instances of IP in 25 patients were identified. Altogether, 11% were grade I (3/28), 54% were grade II (15/28), 25% were grade III (7/28), and 11% were grade IV (3/28). The inflammatory cell population was significantly greater in IP compared with other SPs and greater in grades I and II IP when compared with grade III and IV IP.

Inflammatory cells were identified as a significant cell population in IP, whereas it was less commonly encountered in other forms of SP. The proposed IP staging system may serve as the foundation for improved understanding of IP and, ultimately, may help to predict recurrence or apparent malignant transformation.