[New histological terminology of vulvar intraepithelial neoplasia]

The International Society for the Study of Vulvar Disease (ISSVD) recommends not to use a grading any more and to include in the term vulvar intraepithelial neoplasia (VIN), usual type, the previously called VIN 2 where the nuclear atypia and mitotic figures are confined to the basal half of the epithelium and VIN 3 where nuclear abnormalities and abnormal mitotic figures are present throughout most or all of the thickness of the epithelium. VIN, usual type, is related to a human papillomavirus (HPV) high-risk type infection in most of the cases. The histologic changes previously encompassed within the term VIN 1 will be described as flat condyloma or HPV effect. The less common type of VIN lesion is termed VIN, differentiated type, previously called "high grade" differentiated type or VIN simplex type. This type of VIN is a highly differentiated lesion. The atypia is confined to the basal and parabasal layers of the epithelium, where the cells have abundant cytoplasm and form abortive pearls and the nuclei are relatively uniform in size and contain coarse chromatin and prominent nucleoli. The epithelium does not contain koilocytosis because it is not associated with HPV. It is seen primarily in older women, with a previous history of lichen sclerosus. The diagnosis is often made late in association with keratinising squamous cell carcinomas.