Differentiation-related p53 protein expression in nondysplastic sinonasal inverted papillomas

To clarify p53 protein expression in nondysplastic sinonasal inverted papillomas, archived surgical specimens from 19 patients were studied using immunohistochemistry. Staining results were compared between inverted papillomas and adjacent, nonpapillomatous nasal mucosa. Further, immunoreactivity was compared between columnar (respiratory), transitional (cuboidal), and squamous epithelium in inverted papillomas. Positive staining was found in 17 of 19 inverted papillomas (89%). Immunoreactivity involved predominantly basal and parabasal cells and was either comparable or higher in inverted papillomas compared with adjacent mucosa. In 65% of immunoreactive inverted papillomas comparable staining results were seen between columnar (respiratory), transitional (cuboidal), and squamous epithelium. In 35% of p53 protein-positive inverted papillomas, enhanced immunoreactivity was observed in transitional (cuboidal) and squamous epithelium compared with columnar (respiratory) epithelium. Within these cases, immunoreactivity was either comparable or higher in squamous compared with transitional (cuboidal) epithelium. Conclusively, the expression of p53 protein is present in 89% of nondysplastic sinonasal inverted papillomas and also involves the adjacent, nonpapillomatous nasal mucosa. A tendency toward increasing p53 protein expression from nonpapillomatous nasal mucosa to inverted papilloma as well as along the metaplastic process from columnar (respiratory) to transitional (cuboidal) and finally squamous epithelium within inverted papillomas can be postulated.