Investigating a cluster of vulvar cancers in young women: distribution of human papillomavirus and HPV-16 variants in vulvar dysplastic or neoplastic biopsies

Abstract

Background A high incidence of vulvar cancer, and its precursor lesion, high-grade vulvar intraepithelial neoplasia (VIN) has been identified in young Indigenous 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 distribution and p16INK4aexpression in stored vulvar cancer and high-grade VIN biopsy specimens from women residing in Arnhem Land, with specimens taken from Indigenous and non-Indigenous women in other regions of NT where there is no observed increase in vulvar cancer incidence. Methods: Twenty high-grade VIN and 10 invasive cancer biopsies were assessed from Arnhem Land along with 24 high-grade VIN and 10 invasive cancer biopsies from other regions of NT. Results: Biopsies from Arnhem Land were similar to those from other 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 European prototype. Conclusion: Comparison of biopsies revealed no significant difference in the frequency of oncogenic HPVs or HPV-16 variant types between Arnhem Land and other regions, suggesting another cofactor in this cluster.