Background: A high incidence of vulvar cancer, and its precursor lesion,high-grade vulvar intraepithelial neoplasia (VIN) has been identified in youngIndigenous women living in the Arnhem Land region of the Northern Territory(NT) of Australia. This clustering is restricted to women aged <50 years,suggesting that oncogenic human papillomavirus (HPV) is a key causal factor.This study compared the HPV genotype prevalence, HPV-16 variant distributionand p16INK4aexpression in stored vulvar cancer and high-grade VIN biopsyspecimens from women residing in Arnhem Land, with specimens taken fromIndigenous and non-Indigenous women in other regions of NT where there is noobserved increase in vulvar cancer incidence.
Methods: Twenty high-grade VIN and 10 invasive cancer biopsieswere assessed from Arnhem Land along with 24 high-grade VIN and 10 invasivecancer biopsies from other regions of NT.
Results: Biopsies from Arnhem Land were similar to those fromother regions in the detection of high-risk (HR) or possible HR HPV (VIN: 95%and 84% respectively for Arnhem Land and other regions, P = 0.356; invasive cancer: 100% and 80%, P = 0.473), HPV-16 (VIN: 60% and 80%, P = 0.364; invasive cancer: 70% and 70%, P = 1.0) and p16INK4a expression(VIN: 90% and 84%, P = 0.673; invasive cancer: 100% and 80%, P = 0.474). All HPV-16 variants were of the Europeanprototype.
Conclusion: Comparison of biopsies revealed no significantdifference in the frequency of oncogenic HPVs or HPV-16 variant types betweenArnhem Land and other regions, suggesting another cofactor in this cluster.