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Vulval intraepithelial neoplasia

What is vulval intraepithelial neoplasia?

Vulval (or vulvar) intraepithelial neoplasia is a pre-cancerous skin lesion of any part of the vulva. Vulval intraepithelial neoplasia (VIN) is now also called squamous intraepithelial lesion (SIL). This page mainly refers to VIN, but both terms are currently in use.

VIN was previously known as Bowen disease of the vulva, but this term is no longer used.

VIN is not invasive cancer but vulval squamous cell cancer (SCC) occurs in about 15% of women if VIN is left untreated.

The term VIN excludes vulval extramammary Paget disease and vulval in-situ melanoma.

How does VIN present?

Most women diagnosed with VIN present with the following symptoms:

Images of VIN

Why does VIN occur and who is at risk?

VIN may occur in women of all ages, although currently an increased number of younger women (even teenagers) are presenting with the condition. The average age of women with VIN is 45-50 years.

The following factors have been associated with VIN:

VIN has no association with fertility.

How is VIN diagnosed?

The clinical appearance of an irregular red, white or pigmented plaque on the vulva may suggest a diagnosis of VIN. Colposcopy (examination using magnification and a special light) may be used to see the extent of the condition. A skin biopsy is required to confirm the diagnosis and identify invasive cancer. Warty lesions in postmenopausal women should undergo biopsy, particularly if they do not resolve with simple treatment.

Classification of VIN

Traditionally, pathologists classified VIN into 3 grades: VIN 1, 2 or 3, in keeping with cervical intraepithelial neoplasia (CIN 1, 2, 3).

In 2004, the International Society for the Study of Vulvovaginal Diseases (ISSVD) reclassified VIN. They recommended that the term VIN 1, previously used to describe a mild change in the lower epithelial lining, should no longer be used, as these changes have been found to be due to irritation or non-precancerous viral wart infection and often clear up without treatment. The ISSVD recommended that the term VIN should be used for high-grade abnormal squamous lesions (these were previously known as VIN 2 and VIN 3).

VIN (usual-type or undifferentiated type) can be described by the pathologist as warty, basaloid or mixed VIN. These types of VIN are due to infection with cancer-forming (oncogenic) types of human papillomavirus (HPV) and are more likely to occur in women who smoke. It can be solitary or multicentric.

A less common ‘differentiated’ type of VIN is not caused by human papillomavirus and is associated with rapidly growing squamous cell carcinoma. It arises in about 5% of women with lichen sclerosus or lichen planus. It is usually solitary.

VIN, unclassified type, is rare and is of unknown origin.

Classification of SIL

In 2012, a consensus committee of the College of American Pathologists and the American Society for Colposcopy (the LAST Committee) preferred the term squamous intraepithelial lesion (SIL) to vulval intraepithelial neoplasia (VIN). This classification was accepted by World Health Organisation (WHO) in 2014.

The LAST Committee recognised two grades.

High-grade SIL has potential to progress to invasive SCC, whereas low-grade lesions are low risk.

What treatments are available for VIN?

Usually VIN lesions are treated to reduce the risk of developing invasive cancer. The aim is to remove all affected tissue with a margin of apparently unaffected tissue. This may be done by surgical excision. Sometimes a complete vulvectomy is undertaken because of the extent of disease or because of several independent areas of VIN.

If cancer is not suspected, laser ablation may be used in some centres, and is usually carried out under a general anaesthetic.

Medical therapy reported to be effective in at least some cases of VIN, and is useful for treating a field area prone to multifocal disease. Options include:

None of these medical treatments are officially approved for VIN. Unfortunately recurrence of VIN occurs in at least one-third of patients. This is more likely if:

Prevention of VIN

Immunisation with HPV vaccine has been shown to decrease the risk of VIN as well as cervical cancer and genital warts.

Women that have had genital warts or previous VIN should be strongly encouraged to stop smoking.

Effective treatment of vulval skn disorders such as lichen sclerosus may reduce the risk of VIN and vulval cancer.

What is the outcome for women with VIN?

If left untreated, low-grade VIN may go away by itself (especially the type of low-grade VIN/SIL previously known as Bowenoid papulosis). High-grade VIN may turn into an invasive cancer in later years. On average it takes well over a decade for HPV-associated usual VIN to progress to cancer, but cancer may develop more rapidly in differentiated VIN.

Careful follow-up after treatment is essential long term. VIN may recur, particularly if excision margins are inadequate. Follow-up every 6 to 12 months is recommended for at least 5 years after surgery for VIN.

Up to 50% of women with VIN develop cervical intraepithelial neoplasia (CIN), anal intraepithelial neoplasia (AIN), vaginal intraepeithelial neoplasia (VAIN) or invasive cancer of the genital tract or anus. It is particularly important to have regular cervical smears.

Related information

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Author: Vanessa Ngan, staff writer

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