Human topoisomerase II-α is highly expressed in sinonasal-inverted papilloma, but not in inflammatory polyp

Sinonasal-inverted papilloma is a benign tumour with a high rate of recurrence, but possible malignant transformation. Therefore, investigation of predisposition to malignant transformation of sinonasal-inverted papilloma gives clinicians the opportunity for adequate treatment. Topoisomerase II-alpha (topoII-alpha) and Ki67 are markers of cell proliferation in both normal and neoplastic tissues and its level o expression could be used as a predictive parameter. Our goal was to investigate by immunochemistry the expression level of topoII-in inverted papilloma, inflammatory nasal polyp and normal sinonasal epithelium and to compare it with expression level of Ki67. TopoI alpha nuclear immunostaining showed a differential positivity in the investigated cases. The topoII-alpha index was 30.6 +/- 12.8 in inverte papilloma, 10.7 +/- 6.6 in the adjacent epithelium of inverted papilloma, but only 2.3 +/- 2.0 in the normal sinonasal epithelium. The differences in topoII-alpha expression between inverted papilloma and normal sinonasal epithelia were statistically significant. In inflammatory nasal polyp group, topoII-alpha index was 2.4 +/- 2.1, and the difference in the topoII-alpha index between inverted papilloma and inflammatory polyp group was also statistically significant. Nuclear immunostaining for Ki67 followed a similar variation. The Ki67 index was 50.0 +/- 20. in inverted papilloma, 9.0 +/- 6.6 in the adjacent epithelium of inverted papilloma and 2.4 +/- 0.9 in normal sinonasal epithelium. The differences in Ki67 expression between inverted papilloma and either adjacent or normal sinonasal epithelia were statistically significant. Significant correlation coefficients were found between topoII-alpha and epithelial thickness (r = 0.70, P > 0.0001), and between Ki67 index and epithelial thickness (r = 0.71, P> 0.0001). In the inflammatory nasal polyp group Ki67 index was 5.9 +/- 3.4. The difference in th Ki67 index between inverted papilloma and inflammatory nasal polyp groups was statistically significant. Significant correlation coefficient was found between topoII-alpha index and Ki67 index in inverted papilloma (r = 0.42, P > 0.05). These results suggest that the inverte papilloma contains a significantly higher cell population with proliferative activity by comparison with normal sinonasal and inflammatory polyp epithelia, showing a significant correlation between topoII-alpha and Ki67 expression, and indicating that topoII-alpha could be a independent prognostic factor for a putative malignant transformation.