Differentiation-related p53 protein expression in nondysplastic sinonasal inverted papillomas

To clarify p53 protein expression in nondysplastic sinonasal inverted papil lomas, archived surgical specimens from 19 patients were studied using immu nohistochemistry. Staining results were compared between inverted papilloma s and adjacent, nonpapillomatous nasal mucosa. Further, immunoreactivity wa s compared between columnar (respiratory), transitional (cuboidal), and squ amous epithelium in inverted papillomas. Positive staining was found in 17 of 19 inverted papillomas (89%). Immunoreactivity involved predominantly ba sal and parabasal cells and was either comparable or higher in inverted pap illomas compared with adjacent mucosa. In 65% of immunoreactive inverted pa pillomas comparable staining results were seen between columnar (respirator y), transitional (cuboidal), and squamous epithelium. In 35% of p53 protein -positive inverted papillomas, enhanced immunoreactivity was observed in tr ansitional (cuboidal) and squamous epithelium compared with columnar (respi ratory) epithelium. Within these cases, immunoreactivity was either compara ble or higher in squamous compared with transitional (cuboidal) epithelium. Conclusively, the expression of p53 protein is present in 89% of nondyspla stic sinonasal inverted papillomas and also involves the adjacent, nonpapil lomatous nasal mucosa. A tendency toward increasing p53 protein expression from nonpapillomatous nasal mucosa to inverted papilloma as well as along t he metaplastic process from columnar (respiratory) to transitional (cuboida l) and finally squamous epithelium within inverted papillomas can be postul ated.