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

Association between human papillomavirus infection and malignant transformation of sinonasal inverted papilloma: A systematic review and meta-analysis

PURPOSE

Although sinonasal inverted papilloma malignant transformation has not been entirely understood, some studies have suggested that human papillomavirus acts as a potential oncogenic agent in the progression of sinonasal inverted papilloma to squamous cell carcinoma. The purpose of this study was to assess the association between human papillomavirus infection and sinonasal inverted papilloma transformation, taking also into account human papillomavirus types and their distribution in different geographic areas.

MATERIALS AND METHODS

The literature from the last 25 years was examined. The systematic review and meta-analysis were performed according to the PRISMA guidelines.

RESULTS

A total of 163 malignant sinonasal inverted papilloma and 961 non-malignant sinonasal inverted papilloma were included in the overall analysis. From this sample it was possible to recognize a statistically significant increase in risk of malignancy of sinonasal inverted papilloma for human papillomavirus infection (OR = 2.43, 95 % CI: 1.45-4.08, I2 = 14.0 %). A positive association for patients with high-risk human papillomavirus types was noted (OR = 10.20, 95 % CI: 3.66-28.42, I2 = 15.9 %). In all the 3 geographical areas analyzed the presence of high-risk human papillomavirus significantly increased the probability of malignant transformation.

CONCLUSIONS

High-risk human papillomavirus infection plays a key role in the malignant transformation of sinonasal inverted papilloma and its research during histological examination can be of paramount importance. More prospective studies are needed to help further tease out this association.

Impact of human papillomavirus in sinonasal cancer-a systematic review

BACKGROUND

Human papillomavirus (HPV) is an established prognostic marker in oropharyngeal squamous cell carcinoma. Currently, the role of HPV in sinonasal carcinoma is being explored.

OBJECTIVES

This systematic review addresses the role of HPV in sinonasal cancer, establishing the occurrence of HPV-positive cancers and the influence of HPV-positivity on prognosis in sinonasal cancer as well as the utility of the putative surrogate marker of HPV (p16) in sinonasal cancer.

MATERIAL AND METHODS

Studies were identified with searches of Medline via PubMed and Embase via OVID (4 May 2020). Articles on original research concerning sinonasal cancer and HPV in humans written in English were included. Case reports with less than five cases were excluded.

RESULTS

Initially, 545 articles were identified; 190 duplicate articles were removed leaving 355 articles for title/abstract screening. Title/abstract screening excluded 243 articles, leaving 112 studies assessed for eligibility. After full-text screening, 57 studies were included. All articles investigated the significance of HPV in sinonasal carcinomas. HPV was reported in approximately 30% of sinonasal squamous cell carcinoma (SNSCC), where it was associated with a better prognosis. In sinonasal cancer, p16 is associated with diagnostic pitfalls and a putative utility of p16 in SNSCC has yet to be established. HPV was not frequently reported in other types of sinonasal carcinomas, besides the recently described subtype, HPV-dependent Multiphenotypic Sinonasal Carcinoma. In other types of sinonasal carcinoma, HPV is not frequently found.

CONCLUSION

Approximately 30% of SNSCC are HPV-positive. HPV-positivity in SNSCC is associated with improved survival. HPV occurs only rarely in other sinonasal cancers. There is currently not sufficient evidence for p16 as a surrogate marker of HPV in SNSCC.

Role of High-Risk HPV Detected by PCR in Malignant Sinonasal Inverted Papilloma: A Meta-Analysis

INTRODUCTION

Prior studies suggest that there may be a link between human papillomavirus (HPV) infection and malignant sinonasal inverted papilloma (SNIP). This systematic review and meta-analysis was performed to further evaluate this potential association.

STUDY DESIGN

Systematic review with meta-analysis.

METHODS

The Medline and Embase databases were used to identify case-control studies reporting the risk of malignant SNIP in patients with high-risk HPV subtypes identified by polymerase chain reaction (PCR). Meta-analysis was performed to determine pooled odds ratios (ORs) and 95% confidence intervals (CI).

RESULTS

Twenty-one studies were identified, including a total of 841 subjects with SNIP. Seventeen studies were included in the final analysis, as four studies did not have any HPV-positive tumors in either group. A total of 56 malignant SNIP and 551 benign SNIP were ultimately identified. The pooled log-OR was 1.80 (95% CI: 1.03-2.57) for all high-risk HPV subtypes. Stratification by high-risk HPV subtype showed a log-OR of 1.67 (95% CI: 0.88-2.46) for HPV-16 and log-OR of 2.68 (95% CI: 1.30-4.05) for HPV-18.

CONCLUSION

Infection with high-risk HPV subtypes may be associated with an increased risk of malignant SNIP. HPV-18 showed the greatest overall average effect size of the common high-risk subtypes.

LEVEL OF EVIDENCE

n/a Laryngoscope, 2021.

Human Papillomavirus in Sinonasal Squamous Cell Carcinoma: A Systematic Review and Meta-Analysis

Simple Summary

The causative role of human papillomavirus (HPV) in sinonasal squamous cell carcinoma (SNSCC) remains unclear and is hindered by small studies using variable HPV detection techniques. This meta-analysis aims to provide an updated overview of HPV prevalence in SNSCC stratified by detection method, anatomic subsite, and geographic region. From 60 eligible studies, an overall HPV prevalence was estimated at 26%. When stratified by detection method, HPV prevalence was lower when using multiple substrate testing compared to single substrate testing. Anatomic subsite HPV prevalence was higher in subsites with high exposure to secretion flow compared to low exposure subsites. HPV prevalence in SNSCC followed the global distribution of HPV+ oropharyngeal squamous cell carcinoma. Taken together, this meta-analysis further supports a role for HPV in a subset of SNSCCs.

Abstract

Human papillomavirus (HPV) drives tumorigenesis in a subset of oropharyngeal squamous cell carcinomas (OPSCC) and is increasing in prevalence across the world. Mounting evidence suggests HPV is also involved in a subset of sinonasal squamous cell carcinomas (SNSCC), yet small sample sizes and variability of HPV detection techniques in existing literature hinder definitive conclusions. A systematic review was performed by searching literature through March 29th 2020 using PubMed, Embase, and Web of Science Core Collection databases. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed by two authors independently. A meta-analysis was performed using the random-effects model. Sixty studies (n = 1449) were eligible for statistical analysis estimating an overall HPV prevalence of 25.5% (95% CI 20.7–31.0). When stratified by HPV detection method, prevalence with multiple substrate testing (20.5%, 95% CI 14.5–28.2) was lower than with single substrate testing (31.7%, 95% CI 23.6–41.1), highest in high-exposure anatomic subsites (nasal cavity and ethmoids) (37.6%, 95% CI 26.5–50.2) vs. low-exposure (15.1%, 95% CI 7.3–28.6) and highest in high HPV+ OPSCC prevalence geographic regions (North America) (30.9%, 95% CI 21.9–41.5) vs. low (Africa) (13.1, 95% CI 6.5–24.5)). While small sample sizes and variability in data cloud firm conclusions, here, we provide a new reference point prevalence for HPV in SNSCC along with orthogonal data supporting a causative role for virally driven tumorigenesis, including that HPV is more commonly found in sinonasal subsites with increased exposure to refluxed oropharyngeal secretions and in geographic regions where HPV+ OPSCC is more prevalent.

Role of microRNA-296-3p in the malignant transformation of sinonasal inverted papilloma

Inverted papilloma (IP) is a benign tumor occurring in the nasal cavity and paranasal sinuses. It is reported that 5-15% of IPs undergo malignant transformation into squamous cell carcinoma (SCC), and the role of microRNAs (miRNA/miR) in this process remains to be elucidated. In the present study, whole miRNA profiles using samples of IP and SCC were investigated, in order to detect the function of miRNA in the carcinogenesis of IP. Samples from IPs (n=5) and SCC lesions (n=5), which arose from IPs, were used for miRNA analysis. A total of 200 miRNAs exhibited a >2-fold differential expression between IP and SCC. miR-296-3p was markedly upregulated in SCC with a 23-fold difference. Computational analysis indicated that miR-296-3p targeted PTEN, which regulates the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) signaling pathway and PTEN is involved in the carcinogenesis of SCC. miR-296-3p directly regulated PTEN expression in head and neck cancer cells, with PTEN protein levels decreased in 4/19 the SCCs (21.0%), as compared with those in the IPs (76.4%). Positive p21 staining was observed in 64.7% of IPs; this was a significantly increased rate compared with that for SCCs (26.3%, P=0.0086). The results of the present study indicated that there were marked changes in the miRNA expression signature during the malignant transition. miR-296-3p may serve an important role in the malignant transformation of IPs via the regulation of PTEN, combined with the subsequent inhibition of the PI3K/Akt signaling pathway, and may be a novel agent for cancer prevention.

Clinical effects of p53 overexpression in squamous cell carcinoma of the sinonasal tract: A systematic meta-analysis with PRISMA guidelines

BACKGROUND

The level of p53 protein expression in sinonasal squamous cell carcinoma (SNSCC) has been estimated, but the results remain inconsistent and the point of consensus has not been reached. This study was first determined to evaluate the clinical effects of p53 expression in SCC of the sinonasal tract.

METHODS

According to the preferred reporting items for systematic reviews and meta-analyses (PRISMA) statement criteria, the potential literature was searched from diverse databases. The pooled odds ratios (ORs) with corresponding 95% confidence intervals (CIs) were calculated to assess the strength of association between p53 expression and SNSCC.

RESULTS

Final 17 eligible studies were included in a total of 258 cases and 748 controls. The result of p53 expression was shown to be notably higher in SNSCC than in benign sinonasal papillomas and normal sinonasal mucosa (OR = 26.93, P < 0.001; OR = 39.79, P < 0.001; respectively). Subgroup analyses of ethnicity revealed that p53 expression had significant association with SNSCC in Asian and Caucasian populations in cancer versus benign sinonasal papillomas or normal sinonasal mucosa. The expression of p53 was notably higher in moderately or poorly differentiated SNSCC than in well-differentiated SNSCC (OR = 3.51, P = 0.021), while p53 expression was not associated with histological type.

CONCLUSION

The results suggested that p53 overexpression may be correlated with the carcinogenesis and progression of SNSCC. The p53 gene may become a novel drug target of SNSCC. Additional studies on the correlation of p53 expression with clinicopathological features are needed.

Transcriptionally Active High-Risk Human Papillomavirus is Not a Common Etiologic Agent in the Malignant Transformation of Inverted Schneiderian Papillomas

The role of human papillomavirus (HPV) as an etiologic and transformational agent in inverted Schneiderian papilloma (ISP) is unclear. Indeed, reported detection rates of HPV in ISPs range from 0 to 100%. The true incidence has been confounded by a tendency to conflate high- and low-risk HPV types and by the inability to discern biologically relevant from irrelevant HPV infections. The recent development of RNA in situ hybridization for high-risk HPV E6/E7 mRNA now allows the direct visualization of transcriptionally active high-risk HPV in ISP, providing an opportunity to more definitively assess its role in the development and progression of ISPs. We performed p16 immunohistochemistry and high-risk HPV RNA in situ hybridization on 30 benign ISPs, 7 ISPs with dysplasia, 16 ISPs with carcinomatous transformation, and 7 non-keratinizing squamous cell carcinomas (SCCs) with inverted growth that were unassociated with ISP. Transcriptionally active HPV was not detected in any of the 52 ISPs including those that had undergone carcinomatous transformation, but it was detected in two of seven (29%) non-keratinizing SCCs that showed inverted growth. There was a strong correlation between high-risk HPV RNA in situ hybridization and p16 immunohistochemistry (97%; p < 0.01). These results indicate that transcriptionally active high-risk HPV does not play a common role in either the development of ISP or in its transformation into carcinoma.

Human papillomavirus infection and the malignant transformation of sinonasal inverted papilloma: A meta-analysis

A growing number of molecular epidemiological studies have been conducted to evaluate the association between human papillomavirus (HPV) infection and the malignancy of sinonasal inverted papilloma (SNIP). However, the results remain inconclusive. Here, a meta-analysis was conducted to quantitatively assess this association. Case-control studies investigating SNIP tissues for presence of HPV DNA were identified. The odds ratios (ORs) and 95% confidence intervals (CIs) were calculated by the Mantel-Haenszel method. An assessment of publication bias and sensitivity analysis were also performed. We calculated a pooled OR of 2.16 (95% CI=1.46-3.21, P<0.001) without statistically significant heterogeneity or publication bias. Stratification by HPV type showed a stronger association for patients with high-risk HPV (hrHPV) types, HPV-16, HPV-18, and HPV-16/18 infection (OR=8.8 [95% CI: 4.73-16.38], 8.04 [95% CI: 3.34-19.39], 18.57 [95% CI: 4.56-75.70], and 26.24 [4.35-158.47], respectively). When only using PCR studies, pooled ORs for patients with hrHPV, HPV-16, and HPV18 infection still reached statistical significance. However, Egger's test reflected significant publication bias in the HPV-16 sub-analysis (P=0.06), and the adjusted OR was no longer statistically significant (OR=1.65, 95%CI: 0.58-4.63). These results suggest that HPV infection, especially hrHPV (HPV-18), is significantly associated with malignant SNIP.

Human papillomavirus infection and immunohistochemical expression of cell cycle proteins pRb, p53, and p16(INK4a) in sinonasal diseases

Background

We aimed to clarify the possible role of human papillomavirus (HPV) infection in the malignant transformation of sinonasal inverted papilloma (IP).

Methods

Subjects comprised 32 patients with chronic rhinosinusitis (CRS), 17 with IP, 5 with IP and squamous cell carcinoma (IP + SCC), and 16 with primary sinonasal SCC. HPV presence, viral loads, and physical status were investigated using polymerase chain reaction. Retinoblastoma (pRb), p53, and p16^INK4a gene products were investigated by immunohistochemistry.

Results

HPV DNA was detected in 6.3 % of cases with CRS, 29.4 % with IP, 40 % with IP + SCC, and 25 % with SCC. IP cases had significantly higher HPV presence than CRS cases (p = 0.04). High-risk HPV-16 was the most frequently encountered subtype (10/13, 76.9 %). HPV-16 viral loads varied from 2.5 to 7953 E6 copies/50 ng genomic DNA. Patients in the SCC and IP + SCC groups had significantly higher viral loads than those in the IP and CRS groups (p < 0.01). All SCC and IP + SCC patients with HPV-16 demonstrated mixed-type integration, whereas 4 of 5 HPV-16 patients in the IP and CRS groups showed episomal type infection (p = 0.04). Positivity to pRb was found in 78.1 % of CRS, 35.3 % of IP, and 68.8 % of SCC cases. The presence of HPV DNA negatively correlated with pRb expression in SCC (p = 0.029) and IP (P = 0.049) groups. Although 62.5 % of SCC cases exhibited p53 positivity, only 5.9 % of IP, and no CRS cases were positive. Regardless of HPV status, p16^INK4a positivity was frequently detected in IP cases (82.4 %), less in SCC (12.5 %) cases, and was not detected in the CRS group. Neither the IP nor SCC cohorts showed any correlation between HPV presence and the expression of either p53 or p16^INK4a.

Conclusions

HPV infection was more frequent in the IP, IP + SCC, and SCC groups than the CRS group. Higher viral loads and integration observed in the IP + SCC and SCC groups, and an inverse correlation between HPV presence and positive pRb indicated that persistent infection and integration play a part in tumorigenesis and malignant transformation in certain IP cases. However, p16^INK4a is not a reliable surrogate marker for HPV infection in IP.

Evaluation of correlation of cell cycle proteins and Ki-67 interaction in paranasal sinus inverted papilloma prognosis and squamous cell carcinoma transformation

The recurrent sinonasal inverted papilloma (IP) could be transformed to sinonasal squamous cell carcinoma. We use protein expression patterns by immunohistochemical method to see whether the expression of p53, p16, p21, and p27 belongs to cell-cycle-regulators and PCNA (proliferating cell nuclear antigen) and Ki-67 the proliferation markers in sixty patients with sinonasal inverted papilloma, and 10 of them with squamous cell carcinoma transformation. Significantly elevated levels of Ki-67, p27, and PCNA in IP with squamous cell carcinoma transformation of sinonasal tract compared with inverted papilloma were revealed. No variation of p16, p21, PLUNC (palate, lung, and nasal epithelium clone protein) and p53 expression was correlated to sinonasal IP malignant transformation by multivariate survey. However, we found elevated PLUNC expression in IPs with multiple recurrences. Finally, we found that PCNA, p27 may interact with CDK1 which promote IP cell proliferation and correlate to sinonasal squamous cell carcinoma. Ki-67 could work throughout the cell cycles to cause malignant transformation. In conclusion, this is a first study showing the correlation of Ki-67, PCNA interacted with CDK1 might lead to malignant transformation. Elevated PLUNC expression in the sinonasal IPs was related to multiple recurrences in human.

Gamma irradiation and targeted radionuclides enhance the expression of the noradrenaline transporter transgene controlled by the radio-inducible p21(WAF1/CIP1) promoter

The use of radiation-inducible promoters to drive transgene expression offers the possibility of temporal and spatial regulation of gene activation. This study assessed the potential of one such promoter element, p21(WAF1/CIP1) (WAF1), to drive expression of the noradrenaline transporter (NAT) gene, which conveys sensitivity to radioiodinated meta-iodobenzylguanidine (MIBG). An expression vector containing NAT under the control of the radiation-inducible WAF1 promoter (pWAF/NAT) was produced. The non-NAT expressing cell lines UVW (glioma) and HCT116 (colorectal cancer) were transfected with this construct to assess radiation-controlled WAF1 activation of the NAT gene. Transfection of UVW and HCT cells with pWAF/NAT conferred upon them the ability to accumulate [(131)I]MIBG, which led to increased sensitivity to the radiopharmaceutical. Pretreatment of transfected cells with γ radiation or the radiopharmaceuticals [(123)I]MIBG or [(131)I]MIBG induced dose- and time-dependent increases in subsequent [(131)I]MIBG uptake and led to enhanced efficacy of [(131)I]MIBG-mediated cell kill. Gene therapy using WAF1-driven expression of NAT has the potential to expand the use of this therapeutic modality to tumors that lack a radio-targetable feature.

Skull base inverted papilloma: a comprehensive review

Skull base inverted papilloma (IP) is an unusual entity for many neurosurgeons. IP is renowned for its high rate of recurrence, its ability to cause local destruction, and its association with malignancy. This paper is a comprehensive review of the reports, studies, and reviews published in the current biomedical literature from 1947 to September 2010 and synthesize this information to focus on its potential invasion to the base of the skull and possible intradural extension. The objective is to familiarize the clinician with the different aspects of this unusual disease. The role of modern diagnostic tools in medical imaging in order to assess clearly the limits of the tumors and to enhance the efficiency and the safety in the choice of a surgical approach is pointed out. The treatment guidelines for IP have undergone a complex evolution that continues today. Radical excision of the tumour is technically difficult and often incomplete. Successful management of IP requires resection of the affected mucosa which could be achieved with open surgery, endoscopic, or combined approach. Radio and chemotherapy were used for certain indications. More optimally research would be a multicenter randomized trials with large size cohorts.

Detection of human papillomavirus in sinonasal carcinoma: systematic review and meta-analysis

Since first suggested (in 1983), the etiological role for human papillomavirus (HPV) in sinonasal carcinomas has been subject to constantly increasing interest. To perform systematic review and formal meta-analysis of the literature reporting on HPV detection in sinonasal squamous cell carcinomas (SCC), literature was searched through May 2012. The effect size was calculated as event rates (95% CI), with homogeneity testing using Cochran Q and I(2) statistics. Meta-regression was used to test the impact of study-level covariates (HPV detection method, geographic origin, papilloma type) on effect size, and potential publication bias was estimated using funnel plot symmetry. Thirty-five studies were eligible, covering 492 sinonasal SCCs from different geographic regions. Altogether, 133 (27.0%) cases tested HPV-positive; effect size 0.305 (95% CI, 0.260-0.355; fixed effects model), and 0.330 (95% CI, 0.249-0.423; random effects model. In meta-analysis stratified by (i) HPV detection technique and (ii) geographic study origin, the between-study heterogeneity was significant only for the latter; P = .526, and P = .0001, respectively. In maximum likelihood meta-regression, HPV detection method (P = .511) and geographic origin of the study (P = .812) were not significant study-level covariates. Some evidence for publication bias was found only among polymerase chain reaction-based studies and among studies from Europe and North America but with negligible effect on summary effect size estimates. In sensitivity analysis, all meta-analytic results were robust to all one-by-one study removals. In formal meta-regression, the variability in HPV detection rates reported in sinonasal SCCs was not explained by the HPV detection method or geographic origin of the study.

Detection of human papillomavirus in sinonasal papillomas: systematic review and meta-analysis

OBJECTIVES/HYPOTHESIS

To perform a systematic review and formal meta-analysis of the literature reporting on HPV detection in sinonasal papillomas. Since first reported in 1983, the etiological role for human papillomavirus (HPV) in sinonasal papillomas has been subject to increasing interest.

STUDY DESIGN

A systematic review, with meta-analysis and formal meta-regression.

METHODS

Literature was searched through April 2012. The effect size was calculated as event rates (95% confidence interval [CI]), with homogeneity testing using Cochran's Q and I(2) statistics. Meta-regression was used to test the impact of study-level covariates (HPV detection method, geographic origin, papilloma type) on effect size, and potential publication bias was estimated using funnel plot symmetry.

RESULTS

Seventy-six studies were eligible covering 1,956 sinonasal papillomas from different geographic regions. Altogether, 760 (38.8%) cases tested HPV-positive; effect size 0.421 (95% CI 0.359-0.485, random effects model). The summary HPV prevalence was highest (65.3%) in exophytic papillomas (EP), followed by inverted papillomas (37.8%) and cylindrical cell papillomas (22.5%). In meta-analysis stratified by 1) HPV detection technique, 2) geographic study origin, and 3) papilloma type, the between-study heterogeneity was significant only for the papilloma types (P = .001). In meta-regression, HPV detection method (P = .102), geographic origin (P = .149), or histological type (P = .240) were not significant study-level covariates. Some evidence for publication bias was found only for studies on EP. In sensitivity analysis, all meta-analytic results were robust to all one-by-one study removals.

CONCLUSIONS

Variability in HPV detection rates in sinonasal papillomas is explained by their histological types (not by HPV detection method or geographic origin of study), but none of the three were significant study-level covariates in formal meta-regression.

Prevalence of human papillomavirus, Epstein-Barr virus, p21, and p53 expression in sinonasal inverted papilloma, nasal polyp, and hypertrophied turbinate in Hong Kong patients

BACKGROUND

The purpose of this study of human papillomavirus (HPV), Epstein-Barr virus (EBV), p21, and p53 in sinonasal inverted papilloma (IP) was to help elucidate its pathogenesis.

METHODS

Seventy-three IPs, 48 nasal polyps, and 85 hypertrophied turbinates were subjected to HPV polymerase chain reaction (PCR) study. Seventy-three IPs, 30 nasal polyps, and 32 hypertrophied turbinates were subjected to EBV in situ hybridization (ISH), p21, and p53 immunohistochemical (IHC) studies.

RESULTS

HPV was positive in 3 of 73 IPs (4.1%). All specimens were EBV negative. In all, 99% of IPs showed strong and diffuse p21 nuclear reactivity. Most nasal polyps and hypertrophied turbinates showed weak to moderate immunoreactivity of the basal and parabasal cells. Only focal p53 immunoreactivity of the basal and parabasal cells was found in 19% of IPs and 40% of nasal polyps.

CONCLUSIONS

HPV prevalence of our IP is low. EBV is not present in IP. High p21 and low p53 expression in IP suggests a non-p53-dependent regulation pathway.

Transcriptional Targeting in Cancer Gene Therapy

Cancer gene therapy has been one of the most exciting areas of therapeutic research in the past decade. In this review, we discuss strategies to restrict transcription of transgenes to tumour cells. A range of promoters which are tissue-specific, tumour-specific, or inducible by exogenous agents are presented. Transcriptional targeting should prevent normal tissue toxicities associated with other cancer treatments, such as radiation and chemotherapy. In addition, the specificity of these strategies should provide improved targeting of metastatic tumours following systemic gene delivery. Rapid progress in the ability to specifically control transgenes will allow systemic gene delivery for cancer therapy to become a real possibility in the near future.

HPV infections in benign and malignant sinonasal lesions

This review updates the evidence that the human papillomavirus (HPV) is involved in the development of benign and malignant sinonasal lesions. Since the early 1980s, when evidence was provided on the possible involvement of HPV in the aetiology of both benign respiratory papillomas and squamous cell carcinomas, a substantial number of studies have explored this issue. To date, 33.3% of sinonasal papillomas and 21.7% of sinonasal carcinomas analysed have been shown to be positive for HPV. Many elements of the data parallel the observations made in HPV lesions at other mucosal sites, such as malignant transformation and frequent recurrence after radical treatment; the fact that low risk HPV types 6 and 11 are usually confined to benign lesions, whereas the reverse is true for the oncogenic HPV types 16 and 18; and the presence of squamo-columnar junctions and squamous cell metaplasia in the sinonasal system. The discrepancies reported by several studies might result in part from technical reasons, but it is also possible that sinonasal lesions have a heterogeneous aetiology (HPV related and non-related) and/or that some novel (yet unidentified) HPV types exist in these lesions, which are detected by some studies but not by others.