The role of the human papillomavirus in the pathogenesis of Schneiderian inverted papillomas: an analytic overview of the evidence

Background: Evidence of an etiological role for human papillomavirus (HPV) in Schneiderian inverted papillomas IP arose in the late 1980's; yet almost three decades later, the association between HPV and IP has yet to be universally accepted. This is probably due to the disparate HPV detection rates in IP reported in the literature. We analyzed the weight of published data in order to address the following questions: why do the HPV detection rates in IP vary so greatly? What is the relationship between low-risk (LR) and high-risk (HR) HPV types and HPV detection rates in IP? Is there a relationship between the presence and type of HPV in IP and recurrence and malignant progression?

Materials and methods: A search using the Pubmed search engine was performed to identify studies published in English from 01/87 through 12/06 using the MeSH terms ''HPV'' and ''Inverted", "Exophytic", "Oncocytic Schneiderian" or "Fungiform papilloma''. Data was abstracted from publications including histology, HPV target, HPV type, method of detection, etc. HPV results were stratified by histology and other variables. Tests for heterogeneity (between-study variability) were conducted, and weighted prevalence (WP) estimates and 95% confidence intervals (CI) were calculated using a random-effects inverse-variance model stratified on study. The association between HPV IP recurrence was estimated by random-effects inverse-variance weighted odds ratio (OR).

Results: Weighted estimates revealed similar detection rates across detection methods, 26.8% (95%CI 16.4-37.2%) by ISH, 25.2% (95%CI 14.7-35.6%) by consensus PCR, and 23.6% (95%CI 12.2-35.0%) by type-specific PCR. A preponderance of HPV 6/11 is found in IP as compared to HPV 16/18; the overall unadjusted ratio of LR to high-risk HR HPV types is 2.8:1 The HPV detection rates significantly increase (Wald t-test P < 0.02) in IPs with high-grade dysplasia (WP 55.8%, 95%CI 30.5-81.0%) and carcinoma (WP 55.1%, 95%CI 37.0-73.2%) as compared to IPs with no dysplasia or mild dysplasia (WP 22.3%, 95%CI 15.9-28.6%). Furthermore, the preponderance of LR HPV in benign IP (ratio LR/HR = 4.8:1) shifts in dysplastic and malignant IP. The LR/HR ratio is 1.1:1 for IPs with high-grade dysplasias, this ratio is inverted to favor HR HPV (1:2.4) for malignant IP. Recurrences developed in 44 of 236 patients; HPV was detected in 27 of 44 IPs (WP 57.9%, 95%CI 31.6-84.2%) that developed recurrences and in 24 of 192 IPs (WP 9.7%, 95%CI 4.4-15.0%) that did not develop recurrence. The presence of HPV was significantly associated with the likelihood of developing recurrence (weighted OR of 10.2, 95%CI 3.2-32.8).

Conclusions: We hypothesize that LR HPV may induce IP formation, and then are lost as infected cells are shed, as a "hit and run" phenomenon. HPV detection rates increase in dysplastic IP and SCC-ex-IP with increasing ratio of HR to LR HPV types, compared to nondysplastic IP. We believe that one explanation for the variation in HPV detection rates between different studies may be the actual histologic composition of the cohort. That is, if one series contains a higher frequency of dysplastic and malignant IP, it may have a higher detection rate than another series which contains only nondysplastic IP. We hypothesize that the higher rates of HPV detection in dysplastic and malignant IP may be related to HPV integration. The implication of this is that HPV sub-type testing may identify patients at risk for recurrence, or progression to dysplasia and malignancy, and thus may impact surveillance protocols.