Vulvar intraepithelial neoplasia is a preinvasive skin lesion of the vulva similar to cervical intraepithelial neoplasia (CIN) or dysplasia that can occur in the cervix and result in abnormal Pap smears. i.e., how extensive the abnormal nuclear changes in the skin are. If only the bottom third of the epithelial (skin) lining has these changes, mild dysplasia or VIN I is diagnosed: if the full thickness of the epithelium has abnormal cells, VIN III, also called vulvar carcinoma in situ, is diagnosed. The appearance of VIN II is intermediate between VIN I and VIN III Just like in the cervix, if these vulvar changes are left untreated for many years, some of them turn into an invasive cancer in later years. Therefore doctors recommend excising that abnormal tissue so as to prevent any cancer from developing.