Vaginal intraepithelial neoplasia (VAIN) is a condition that describes premalignant histological findings in the vagina characterized by dysplastic changes.The disorder is rare and generally has no symptoms. VAIN can be detected by the presence of abnormal cells in a Papanicolaou test (Pap smear).Like cervical intraepithelial neoplasia, VAIN comes in three stages, VAIN 1, 2, and 3. In VAIN 1, a third of the thickness of the cells in the vaginal skin are abnormal, while in VAIN 3, the full thickness is affected. VAIN 3 is also known as carcinoma in-situ, or stage 0 vaginal cancer.Infection with certain types of the human papillomavirus ("high-risk types") may be associated with up to 80% of cases of VAIN. Vaccinating girls with HPV vaccine before initial sexual contact has been shown to reduce incidence of VAIN.One study found that most cases of VAIN were located in the upper third of the vagina, and were multifocal. In the same study, 65 and 10% patients with VAIN also had cervical intraepithelial neoplasia and vulvar intraepithelial neoplasia, respectively.In another study, most cases of VAIN went into remission after a single treatment, but about 5% of the cases studied progressed into a more serious condition despite treatment.