Epidemiology of vulvar intra-epithelial neoplasias

The vulvar intraepithelial neoplasia has been identified as one of the 12 neoplasias whose incidence increases in the developed countries. The vulvar intraepithelial neoplasia (VIN) and invasive vulvar cancer incidence increases by 2.4% per annum; and this principally in young women. The VIN account for 57% of the vulvar neoplasias and are actually more frequent than invasive carcinomas. In the United States, between 1973 and 2000, the incidence of the VIN increased by 411% against 20% for invasive cancers. Similar figures were reported from Norwegian registers. The VIN have a different age distribution than invasive cancers: the incidence of the VIN increases until the age of 40-49 years then decreases while the incidence of invasive cancers increases after 50 years without real peak of incidence. The increase in the incidence of VIN could be followed by an increase in the incidence of invasive cancers but the unknowns on the natural history of the VIN and the impact of the treatments make any extrapolation hazardous. The association between the VIN and the human papillomavirus (HPV) has been well established. It should be noted that, contrary to the cervical neoplasia that are related for nearly 100% to the HPV, only 30-40% of invasive cancers of the vulva are related to HPV, while the other carcinomas are related to the evolution of a vulvar lichen sclerous. The HPV induce various types of anogenital lesion according to their genotype. These lesions can be benign for the HPV6 and 11 and preneoplastic or neoplastic for the HPV16 and 18. The presence of HPV16 and 18 is found in 70 to 80% of the VIN suggesting that HPV vaccines could decrease the incidence VIN and HPV related invasive vulvar cancer.