Abstract
Classification of vulvar precancerous lesions is based on the concept of vulvar intraepithelial neoplasia (VIN). Two basic types of VIN are recognized histologically: VIN of the usual type (u-VIN) and VIN of the differentiated type (d-VIN).
The three grade evaluation system is used to assess the intesity of dysplastic changes in u-VIN (u-VIN I, II and III). The precancerous potential of d-VIN corresponds to carcinoma in situ and therefore grading is not applied. u-VIN is etiologically linked to HPV infection, whereas d-VIN is HPV negative and emerges in the environment of chronic vulvar dermatoses (lichen sclerosus and lichen simplex chronicus). u-VIN has a tendency to multifocality and prolonged recurrent progression to the invasive squamous cell carcinoma.
On the other hand, d-VIN represents rather a solitary lesion with a propensity to the rapid stromal invasion. u-VIN usually affects premenopausal women with a higher incidence of other precancerous lesions of the lower female genital tract including the perineum and anal area. Patients diagnosed with d-VIN are of postmenopausal age without any association with aforementioned dysplastic lesions of other anatomic locations.
The low diagnostic reproducibility of the u-VIN I category, doubts about the precancerous potential of u-VIN I and the problematic distinction between u-VIN II and u-VIN III resulted in the modification of the current terminology. The grading of u-VIN was abandoned, u-VIN II and u-VIN III categories were merged and u-VIN I was removed from the classification scheme.
The revised u-VIN category therefore represents high grade dysplastic lesions associated with HPV infection (former u-VIN II and u-VIN III categories) and the term d-VIN is still reserved for the HPV negative high grade vulvar precancerosis.