by Jason Wasserman MD PhD FRCPC
July 6, 2023
Vulvar intraepithelial neoplasia (VIN) is a precancerous growth arising from the cells on the surface of the vulva. If left untreated, VIN can turn into a type of vulvar cancer called squamous cell carcinoma over time. Another name for VIN is squamous intraepithelial lesion (SIL).
VIN starts from squamous cells normally on the surface of the vulva. The squamous cells form a thin layer of tissue called the epithelium. The term “intraepithelial” means that the abnormal cells in VIN are still located entirely within the epithelium.
Common symptoms of VIN include itchiness and irritation of the vulvar skin. However, a significant number of patients with VIN experience no symptoms, and the condition is discovered during a routine examination.
Most causes of VIN are caused by long-standing infection with human papillomavirus (HPV). Low grade VIN (VIN1) is typically associated with low-risk subtypes of HPV (6, 11, 42, 43, 44) whereas high grade VIN (VIN2 and VIN3) is typically associated with high-risk subtypes of HPV (subtypes 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 66, 68). Differentiated vulvar intraepithelial neoplasia (dVIN) is a type of VIN caused by long-standing inflammation of the vulvar by conditions such as lichen sclerosus.
No. VIN is not a type of cancer. However, VIN is an abnormal growth that can change into a type of vulvar cancer called squamous cell carcinoma over time.
VIN is divided into three categories – VIN1, VIN2, and VIN3 – based on the degree of cytologic atypia (how abnormal the cells look under the microscope), the location of the abnormal cells, and the number and location of mitotic figures (cells dividing to create new cells). The grade is important because the chance of developing vulvar cancer from VIN is much higher for VIN2 and VIN3 compared to VIN1.
The abnormal cells in VIN1 are located within the lower 1/3 of the epithelium. Large abnormal-looking squamous cells called koilocytes are also commonly seen. Another name for VIN1 is low grade squamous intraepithelial lesion (LSIL). VIN1 that sticks out from the surface of the tissue is called condyloma acuminatum.
The abnormal cells in VIN2 involve the lower 2/3 of the epithelium and the cells often appear larger and darker than the cells in VIN1. An increased number of mitotic figures (cells dividing to create new cells) are also typically seen. Another name for VIN2 is high grade squamous intraepithelial lesion (HSIL).
The abnormal cells in VIN3 involve almost the entire epithelium and the cells are larger and darker than the cells in VIN1 or VIN2. A large number of mitotic figures (cells dividing to create new cells) are also typically seen. Another name for VIN3 is high grade squamous intraepithelial lesion (HSIL).
VIN is described as warty type when long finger-like projections of tissue called papillae are seen on the surface of the tissue. Large abnormal-looking squamous cells called koilocytes are also usually seen.
VIN is described as basaloid type when the growth is made up of dark blue cells. These cells are called “basaloid” because they resemble basal cells normally found at the bottom of the epithelium.
Cells infected with high-risk types of human papillomavirus (HPV) produce large amounts of a protein called p16 and increased p16 is commonly seen in VIN2 and VIN3. For this reason, pathologists perform a test called immunohistochemistry that allows them to see if the cells are producing extra p16. Pathologists use the term positive or reactive to describe cells that show increased amounts of p16. A positive result supports the diagnosis of VIN2 or VIN3 and helps exclude other conditions that can look like these conditions under the microscope.