Patterns of p21(waf1/cip1) expression in non-papillomatous nasal mucosa, endophytic sinonasal papillomas, and associated carcinomas

Aims-To clarify p21(waf1/cip1) expression in sinonasal lesions. Methods-Archived surgical specimens from 38 patients were investigated by m eans of immunohistochemistry. p21(waf1/cip1) staining was evaluated in the different layers of the epithelium. In addition, human papillomavirus (HPV) infection and p53 protein overexpression were assessed and correlated with p21(waf1/cip1) expression. Results-p21(waf1/cip1) staining was negative in non-papillomatous nasal muc osa. HPV infection and p53 protein overexpression were not seen. Sixteen of 20 inverted papillomas showed p21(waf1/cip1) expression. HPV infection was found in 16 cases and p53 protein overexpression was present in 13 specime ns. Expression of p21(waf1/cip1) was restricted to surface cells in five ca ses, but involved basal/parabasal cells in 11 specimens. Immunoreactivity f or p21(waf1/cip1) in basal/parabasal cells colocalised with p53 protein ove rexpression. Enhanced expression rates for p21(waf1/cip1) were seen in tran sitional and squamous epithelium compared with columnar epithelium. p21(waf 1/cip1) expression involved only surface cells in cylindrical cell papillom as. HPV infection and p53 protein overexpression were detected in all speci mens. One of five squamous cell carcinomas showed p21(waf1/cip1) expression . HPV infection was seen in two cases, and all carcinomas showed p53 protei n overexpression. Conclusions-Expression of p21(waf1/cip1) is associated with terminal differ entiation in surface cells in inverted papillomas and cylindrical cell papi llomas, but not in non-papillomatous nasal mucosa. Overexpression of p53 pr otein colocalises with p21(waf1/cip1) expression in basal/parabasal cells i n inverted papillomas but not in cylindrical cell papillomas. Expression of p21(waf/cip1) in squamous cell carcinomas involves a subset of tumours wit h p53 protein overexpression.