Vulvar Intraepithelial Neoplasia (VIN): Understanding Your Pathology Report

by Jason Wasserman MD PhD FRCPC
May 22, 2026

Vulvar intraepithelial neoplasia (VIN) is a general term for noncancerous but abnormal changes in the squamous cells that cover the surface of the vulva. The word “intraepithelial” means that the abnormal cells are confined to the top layer of the vulvar skin (the epidermis) and have not grown into the deeper tissue. VIN is not cancer, but some forms of VIN can develop into squamous cell carcinoma of the vulva over time if they are not treated.

The way pathologists describe these conditions has changed. Older pathology reports divided VIN into three grades (VIN1, VIN2, and VIN3). Current pathology reports use updated terms that better reflect what each condition means and how it behaves. This article explains what “VIN” means, how the terminology has changed, and what the current categories are. Because each current category has its own causes, risks, and management, this article also links to a detailed article for each one. If your pathology report uses one of the newer terms, you may wish to go directly to the matching article below.

What does “VIN” mean, and how has the terminology changed?

VIN is an umbrella term that has been used for several different abnormal changes in the surface of the vulva. Over time, research has shown that the older three-grade system (VIN1, VIN2, VIN3) grouped conditions that are actually quite different in their causes and behavior. Current classification systems, used by the International Society for the Study of Vulvovaginal Diseases (ISSVD) and the World Health Organization, divide these conditions into the categories below.

  • VIN1 is now called LSIL — What used to be called VIN1 is now called low grade squamous intraepithelial lesion (LSIL). This change was made because VIN1 is not a true precancer. It is a mild change that reflects an active human papillomavirus (HPV) infection and usually resolves on its own.
  • VIN2 and VIN3 are now called HSIL — What used to be called VIN2 and VIN3 are now grouped together as high grade squamous intraepithelial lesion (HSIL). The separation of VIN2 from VIN3 was found to be unreliable, and both carry a similar, meaningful risk of progressing to cancer. HSIL of the vulva is also sometimes called “usual-type VIN.”
  • Differentiated VIN (dVIN) remains a separate category — Differentiated vulvar intraepithelial neoplasia (dVIN) is a distinct precancerous condition that is not caused by HPV. The term dVIN is used in both older and current pathology reports.

In other words, the older term “VIN” now corresponds to three separate conditions: LSIL, HSIL, and dVIN. Each is described briefly below, with a link to a full article.

What causes vulvar intraepithelial neoplasia?

The conditions grouped under VIN develop along two different pathways:

  • HPV-associated pathway — LSIL and HSIL of the vulva are caused by infection with human papillomavirus (HPV). LSIL is commonly associated with low-risk HPV types (such as HPV6 and HPV11), while HSIL is associated with high-risk HPV types (such as HPV16 and HPV18).
  • HPV-independent pathway — dVIN is not caused by HPV. It is strongly associated with long-standing inflammatory vulvar skin conditions, especially lichen sclerosus.

The types of vulvar intraepithelial neoplasia

Low grade squamous intraepithelial lesion (LSIL)

LSIL of the vulva, previously called VIN1, is the mildest of these conditions. It is caused by HPV and is best understood as a sign of an active HPV infection rather than a true precancer. Under the microscope, the abnormal cells are limited to the lower part of the epidermis and often include HPV-infected cells called koilocytes. Most cases resolve on their own as the immune system clears the HPV infection, and the risk of progression to cancer is very low. When LSIL forms a raised, wart-like growth, it may be called condyloma acuminatum (genital warts). To learn more, read our full article on low grade squamous intraepithelial lesion (LSIL) of the vulva.

High grade squamous intraepithelial lesion (HSIL)

HSIL of the vulva, previously called VIN2 and VIN3 and also known as usual-type VIN, is a precancerous condition caused by high-risk HPV. Under the microscope, the abnormal cells extend through more of the epidermis than in LSIL, and a protein called p16 typically shows strong, continuous “block-type” staining. HSIL carries a meaningful risk of progressing to vulvar cancer if it is not treated, so it is usually treated and monitored. HSIL can show different microscopic patterns, including warty (with wart-like surface projections) and basaloid (made up of small, dark blue cells), but these are descriptions of appearance rather than separate grades. To learn more, read our full article on high grade squamous intraepithelial lesion (HSIL) of the vulva.

Differentiated vulvar intraepithelial neoplasia (dVIN)

dVIN is a precancerous condition that is not caused by HPV. It is strongly associated with long-standing inflammatory skin conditions, particularly lichen sclerosus. dVIN can be difficult to recognize under the microscope because the changes are often subtle, and it typically shows an abnormal pattern of the protein p53. Compared with HSIL, dVIN has a higher risk of progressing to vulvar cancer and tends to progress more quickly, so prompt treatment and close follow-up are important. To learn more, read our full article on differentiated vulvar intraepithelial neoplasia (dVIN).

How are these types different?

The three conditions differ in their cause, their risk of progressing to cancer, and how they are managed:

  • Cause — LSIL and HSIL are caused by HPV. dVIN is not caused by HPV and is linked to lichen sclerosus and other chronic inflammatory skin conditions.
  • Risk of progressing to cancer — LSIL has a very low risk. HSIL has a meaningful risk. dVIN has the highest risk and tends to progress most quickly.
  • Typical age — HSIL tends to occur in younger patients (often 30s to 50s), while dVIN tends to occur in older, postmenopausal patients. LSIL can occur at any age.
  • Microscopic testing — HSIL shows strong, continuous “block-type” p16 staining. LSIL is negative or only patchy for p16. dVIN is typically negative for p16 but shows an abnormal p53 pattern.
  • Management — LSIL often requires only observation. HSIL and dVIN are usually treated, most often with surgical removal, and require ongoing follow-up.

What are the symptoms?

Many people with VIN have no symptoms, and the condition is found during an examination performed for another reason. When symptoms are present, they may include itching, burning, soreness, or irritation of the vulvar skin, or a visible bump, patch, or area of color change. Because symptoms overlap with common, noncancerous skin conditions, any persistent vulvar symptom or new visible change should be examined, especially in someone with a history of HPV-related disease or a chronic vulvar skin condition.

How is the diagnosis made?

VIN is diagnosed when a sample of vulvar skin is examined under the microscope by a pathologist. The sample is usually obtained through a small biopsy taken from the area of concern. To determine which type of VIN is present, the pathologist examines how deeply the abnormal cells extend into the epidermis and often performs additional tests, such as immunohistochemistry. The p16 stain helps identify HPV-associated lesions (LSIL and HSIL), and the p53 stain helps identify dVIN. The specific tests and findings are described in the dedicated article for each condition.

What happens after this diagnosis?

What happens next depends on which type of VIN is present, because the three conditions are managed differently:

  • LSIL — Because LSIL usually resolves on its own, treatment is often not needed. The team may simply monitor the area, and may treat genital warts if they are present and bothersome.
  • HSIL — Because HSIL has a meaningful risk of progressing to cancer, it is usually treated. Options the team may discuss include surgical removal, laser treatment, and topical medications, followed by ongoing monitoring.
  • dVIN — Because dVIN has the highest risk of progressing to cancer, complete surgical removal is generally the goal, along with treatment of any underlying skin condition such as lichen sclerosus and close long-term follow-up.

The dedicated article for each condition describes the treatment options and follow-up in more detail.

Questions to ask your doctor

  • Which type of VIN do I have — LSIL, HSIL, or dVIN?
  • If my report uses an older term such as VIN1, VIN2, or VIN3, what is the current term for my diagnosis?
  • Was my condition caused by HPV, or is it HPV-independent?
  • Was p16 or p53 testing performed, and what did the results show?
  • What is my risk of this condition progressing to vulvar cancer?
  • Do I need treatment, and if so, what are my options?
  • Do I have an underlying skin condition, such as lichen sclerosus, that also needs treatment?
  • How often will I need follow-up examinations?
  • Should I be checked for HPV-related changes in other areas, such as the cervix or anal canal?
  • What symptoms or changes should prompt me to contact you between visits?

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