Differentiated (simplex) vulvar intraepithelial neoplasia: a case report and review of the literature.

Differentiated (simplex) vulvar intraepithelial neoplasia (VIN) is an uncommon variant of VIN characterized by highly differentiated morphology, making it a potential diagnostic pitfall. It may arise in the background of lichen sclerosus, and unlike most VIN, is not causally associated with human papilloma virus infection. It occurs in an older demographic and is thought to be the precursor of aggressive, invasive vulvar squamous cell carcinoma. For this reason, the timely and accurate diagnosis of this unusual lesion is crucial. The clinical and histologic features of a case of a 70-year-old woman with newly diagnosed differentiated (simplex) VIN arising in a background of long-standing lichen sclerosus is reported, and the historic aspects, current terminology, and diagnostic criteria of differentiated (simplex) VIN are reviewed.