label: Vulvar intraepithelial neoplasia
label_lc: vulvar intraepithelial neoplasia
description: "Vulvar intraepithelial neoplasia (VIN) is widely accepted as the precursor lesion of vulvar squamous cell carcinoma (VSCC). VSCC arises via either a human papilloma virus (HPV)-associated pathway, or more commonly, via a mechanism independent of HPV, often being linked to chronic inflammatory conditions such as lichen sclerosus (LS). Accordingly, two distinct subtypes of VIN are recognized: the HPV-associated high-grade squamous intraepithelial lesion/usual VIN (HSIL/uVIN) and the non-HPV-associated differentiated VIN (dVIN). HSIL is clinically identified by its multifocal, warty appearance and on histology by conspicuous cytological and architectural atypia. Differentiated VIN, on the other hand, often produces ill-defined lesions, and on histology, notoriously mimics non-neoplastic epithelial disorders (NNED), particularly LS. As a result, dVIN is rarely identified in advance of a diagnosis of invasive malignancy, despite being the precursor lesion of the majority of VSCC."