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Recurrent respiratory papillomatosis (RRP) is a benign condition that rarely metastasizes as invasive squamous cell carcinoma. Although this disease is associated with human papillomavirus, the role of this virus in tumorigenesis is unclear.The aim of this study is to assess the involvement of the tumor suppressors P16INK4A and p53 in RRP tumor progression.Immunohistochemistry of p16INK4A and p53 was performed on biopsies of recurrent squamous papillomas and invasive lesions in nine patients.Twenty biopsies were graded as papillomas (RP), three as papillomas with high-grade dysplasia/carcinoma in situ (HGD/CIS), and two as invasive squamous cell carcinoma (SCCA). Forty-five percent of RP and 60% of HGD/CIS/SCCA expressed p16INK4A. Fifty percent of RP and 100% of HGD/CIS/SCCA expressed p53. The difference in the frequency of p53-positive staining between HGD/CIS and SCCA (100% of tissues examined) and RP (50% of tissues examined) approached statistical significance. Neither p16INK4A nor p53 was predictive of invasive transformation.Expression of p16INK4A, which is a surrogate for the tumor suppressor retinoblastoma (Rb), did not immediately lead to invasive disease. There is no correlation between disease severity of RRP and level of p16INK4A.