Human papillomavirus (HPV) and p16 expression in the female genital tract and its value in diagnosis.

Background: Two subtypes of vulvar squamous cell carcinomas (VSCC) have previously been defined. The more common keratinising type typically occurs in older women (50- 70 years), is generally associated with lichen sclerosis and/or differentiated vulvar intraepithelial neoplasia (dVIN), and is often associated with p53 tumor suppressor gene mutations. The other subtype is more common in younger women and primarily associated with human papilloma virus (HPV) infection, and a common precursor is usual-type vulvar intraepithelial neoplasia (uVIN) of the basaloid or warty type. To investigate the prognostic significance of HPV status in vulvar squamous cell carcinomas (VSCC) and to determine whether preoperative determination of p16 or p53 status would have clinical relevance. Materials and methods: This is prospective and descriptive study conducted in the Department of Pathology, Government Medical College, Siddipet over a period of 1 year. Immunohistochemistry was performed by using 5 μm paraffin sections which were deparaffinized in xylene (three times for five minutes) and rehydrated in decreasing concentrations of ethanol (100%, 96%; two times each for ten minutes) followed by washing in deionised H2O for one minute. To unmask the p16 antigen the slides were covered with 0.01 M sodium citrate buffer (pH 6.0) and placed on a hot plate (950C) for 10 minutes. After cooling down the specimens were rinsed briefly in deionised H2O (three times). The specific primary (mouse monoclonal) antibody (p16, clone E6H4) was applied in a dilution of 1:50 overnight at 40C. Result: HPV types and status in correlation with clinical parameters and expression of p16. 70 out of 70 patients with PCV could be evaluated for HPV status. 25 were positive for high-risk HPV and 45 were HPV negative. The majority (16 out of 26, 64%) of HPVpositive patients were positive for HPV16. The others were positive for HPV45 (4 patients, 16%), HPV18 (2 patient, 8%), HPV35 (1 patient), HPV56 (1 patient), and HPV68 (1 patient). Human papillomavirus positivity was significantly correlated with strong p16 expression (p= 0.045). In all, 7 out of the 59 HPV-negative patients were negative for p16 immunostaining, while the remaining 83% showed varying expression: 31 out of 45 (68.9%) showed moderate or strong p16 expression. Conclusion: The vast majority of HPV positive vaginal cancers showed p16 overexpression, suggesting active involvement of HPV in the malignant transformation process. HPV vaccines will help prevent some of the primary female genital cancers associated with HPV type 16. More indepth studies are needed to understand the molecular carcinogenesis pathway in these p16-negative tumors and to improve outcomes for this population. [ABSTRACT FROM AUTHOR]