The diagnosis of vaginal intraepithelial neoplasia (VaIN) has increased steadily over the past several decades as a result of heightened awareness, expanded cytologic screening, and the liberal use of colposcopy. The relative rarity of VaIN, which is far less common than cervical intraepithelial neoplasia (CIN) or vulvar intraepithelial neoplasia (VIN), is an impediment to a thorough understanding of the disease process and its natural course. As a result, much of this information is an extrapolation of our knowledge of the pathophysiology of cervical and vulvar intraepithelial neoplasia.
Diagnosis and management of women with VaIN is reviewed here. VIN and CIN are discussed separately. (See "Vulvar intraepithelial neoplasia" and "Cervical intraepithelial neoplasia: Management of low-grade and high-grade lesions" and "Cervical intraepithelial neoplasia: Treatment and follow-up".)
Vaginal intraepithelial neoplasia is defined by the presence of squamous cell atypia without invasion. The disease is classified according to the depth of epithelial involvement: VaIN 1 and 2 involve the lower one-third and two-thirds of the epithelium, respectively, and VaIN 3 involves more than two-thirds of the epithelium (picture 1). Carcinoma in situ, which encompasses the full thickness of the epithelium, is included under VaIN 3. In 2012, as part of the lower anogenital squamous terminology (LAST) standardization project for human papilloma virus (HPV)-associated lesions, the College of American Pathologists and the American Society for Colposcopy and Cervical Pathology have proposed a revised terminology by which VaIN is reported using a two-tiered nomenclature: LSIL for low-grade disease (VaIN 1) and HSIL for high-grade disease .
Intraepithelial vaginal dysplasia of glandular origin, or atypical vaginal adenosis, is a separate entity. This lesion has a well-established association with in utero diethylstilbestrol (DES) exposure and may be a precursor to DES-associated clear-cell adenocarcinoma . In addition, cases have been reported of atypical adenosis and vaginal adenocarcinomas in non-DES-exposed women .
The true incidence of VaIN is unknown, but is estimated at 0.2 to 0.3 cases per 100,000 women in the United States . The average patient is between 43 and 60 years of age [5-7]. Based on data from the United States (US) Centers for Disease Control and Prevention's National Program of Cancer Registries and the National Cancer Institute's Surveillance, Epidemiology and End Results Program, the incidence of vaginal carcinoma in situ in the US is estimated at 0.1 cases per 100,000 women. Vaginal carcinoma in situ incidence peaks at age 70 to 79 years, slightly younger than the peak incidence age for vaginal carcinoma .