Abstract: Objective To explore histogenesis and the relation between expression of p53 and proliferating cell nuclear antigen(PCNA)and prognosis of inverted papilloma of nose and paranasal sinuses. Methods Histologic observation and immunohistochemistry were used to study the histogenic constituent and the expression of p53 and PCNA both qualitatively and quantitatively in 33 inverted papilloma. Results The neoplastic epithelia contains respiratory pseudostratified ciliated columnar、transitional and squamous epithelia and cytokeratin 5&8 immunoreactivity cells;p53 protein positive expression and PCNA LI were significantly related to both dysplasia and malignant transformation of imverted papilloma;The intensity of p53 reaction was correlated to that of PCNA. Conclusion The inverted popilloma was drived from cells of the basal layer of the nasal mucosa;The patiens with p53 protein immunoreactivity positively and high PCNALI have a poor prognosis.