Vaginal Intraepithelial Neoplasia

Abstract

Vaginal squamous intraepithelial neoplasia (VaIN) is uncommon when comparing to the cervical or vulval counterparts. Almost all are caused by infection of human papillomaviruses (HPVs). Traditionally, VaIN was classified into grades I, II, and III, depending on the degree of involvement of the epithelium by the dysplastic cells. The 2013 Lower Anogenital Squamous Terminology (LAST) Standardization Project working group and the World Health Organization (WHO) 2014 classification recommend that lesions that are considered as condyloma and VaIN I should now be classified as low-grade squamous intraepithelial lesions (LSILs). LSIL is a morphological manifestation of transient, usually low-risk HPV infection. VaIN II/III lesions signify persistent infection by high-risk HPV and are considered precancerous; they should now be classified as high-grade squamous intraepithelial lesions (HSILs). The change in nomenclature reduces the problem of interobserver variability in assessing VaIN II and also classifies lesions into two biological and managerial groups. Histological assessment of problematic HSIL may be supported by using several immunohistochemical stains such as p16, ki-67, and ProEx C. Patients with persistent high-risk HPV infection are at an increased risk of recurrence and development into squamous cell carcinoma. Although many studies on HPV-associated lesions were done on the cervix, given the biological similarity between those in the vagina and other lower genital sites, it is conceivable that they can be regarded as closely related lesions even if not a single disease entity. Premalignant glandular lesions of the vagina are rare and a brief account will be given.