Vulval intraepithelial neoplasia

Author: Vanessa Ngan, Staff Writer, 2003. Updated by Hon A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand, September 2015.

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 vulval squamous intraepithelial lesion (SIL). In this article, we abbreviate the condition as VIN/SIL.

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

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

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

How does VIN/SIL present?

Most women diagnosed with VIN/SIL present with the following symptoms:

Images of VIN/SIL

Why does VIN/SIL occur and who is at risk?

VIN/SIL 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/SIL is 45–50 years.

The following factors have been associated with VIN/SIL:

How is VIN/SIL diagnosed?

The clinical appearance of an irregular red, white or pigmented plaque on the vulva may suggest a diagnosis of VIN/SIL. 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/SIL

The classification of VIN/SIL has evolved over a number of years. The terminology adopted by the International Society for the Study of Vulvovaginal Diseases (ISSVD) in 2015 is:

1. Low grade squamous intraepithelial lesion (flat condyloma or HPV effect)
2. High grade squamous intraepithelial lesion (VIN usual type)
3. Intraepithelial neoplasia, differentiated-type

High-grade and differentiated-type SIL have potential to progress to invasive SCC, whereas low-grade lesions are low risk and should not be considered neoplastic.

What treatments are available for VIN/SIL?

Low-grade VIN/SIL does not always require treatment, but follow-up should be arranged until the lesions resolve as they sometimes progress to high-grade VIN/SIL.

High grade and differentiated VIN/SIL 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/SIL.

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/SIL, and is useful for treating a field area prone to multifocal disease. Options include:

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

Prevention of VIN/SIL

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

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

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

What is the outcome for women with VIN/SIL?

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

Careful follow-up after treatment is essential long term. VIN/SIL 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/SIL.

Up to 50% of women with VIN/SIL 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.

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