Vulval intraepithelial neoplasia
What is vulval intraepithelial neoplasia?
(Squamous) vulval (or vulvar) intraepithelial neoplasia is a pre-cancerous skin lesion of any part of the vulva, and was previously known as Bowen disease of the vulva. Vulval intraepithelial neoplasia is often called VIN.
VIN is not invasive cancer but vulval squamous cell cancer occurs in about 15% of women if VIN is left untreated.
How does VIN present?
Most women diagnosed with VIN present with the following symptoms:
- Mild to severe vulvar itching
- Mild to severe vulvar burning
- One or more slightly raised well defined skin lesions that may be pink, red, brown or white in colour.
Why does it occur and who is at risk?
The following factors have been associated with VIN:
- HPV, which also causes genital warts. Only oncogenic types of HPV (especially types 16 and 18) are associated with VIN, and these don't always cause visible warts.
- Smoking; it is thought that the cancer promoting agents in cigarettes are concentrated in the skin of the lower genital tract.
- Immunosuppression by disease or medications.
- Vulval inflammatory skin disease, particularly lichen sclerosus or erosive lichen planus.
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.
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.
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.
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.
VIN, unclassified type, is rare and is of unknown origin.
Some pathologists use other classifications to describe VIN.
What treatments are available?
Usually all VIN lesions are treated to reduce the risk of developing cancer. The mainstay of treatment 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 includes:
- Imiquimod cream, applied 3 times weekly for 12 to 20 weeks. This results in red, inflamed and eroded tissue often accompanied by considerable discomfort.
- 5-fluorouracil cream, applied twice daily for several weeks. This causes quite severe inflammation (several weeks) and will not be tolerated by all women. It is less effective than imiquimod cream.
- Photodynamic therapy (PDT) requires specialised equipment and can also be very painful.
None of these medical treatments are officially approved for 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.
What is the outcome for women with VIN?
If left untreated, VIN may go away by itself (especially the type of VIN known as Bowenoid papulosis) or it may turn into an invasive cancer in later years. On average it takes well over a decade for VIN to go onto cancer.
Careful follow-up after treatment is essential longterm, as VIN may recur in about half of women treated during their lifetime. It grows slowly so most women are reviewed every 6 to 12 months.
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. It is particularly important to have regular cervical smears.