Vulval intraepithelial neoplasia (VIN)

What is it?

Vulval intraepithelial neoplasia (VIN) is a condition where there are pre-cancerous cells in the skin of the vulva. Before discussing VIN it is important to remember that skin is divided into three layers: epidermis, dermis and the fatty layers beneath. The epidermis or top layer is less than one millimetre thick and is constantly being shed. Cells from the bottom layer develop and mature and slowly migrate to the top layer where they are shed.

It takes about 120 days for each individual cell to undergo this process. Beneath the epidermis is the dermis, separated by the basement membrane — this acts as a landmark between the two layers. The dermis is much thicker and contains hair follicles, glands (which make skin greasy) and structures which detect sensations such as temperature changes, touch and pressure. Beneath the dermis is the fatty layer which improves body insulation and contains the main blood vessels which supply oxygen to the upper layers.

In VIN, the pre-cancer cells are located within the epidermis or the very top layer and are only a millimetre or so thick. The abnormal cells do not penetrate deep down into the dermis so as a consequence, it is easy to see on the surface of the skin with the naked eye the affected areas. We use the word pre-cancer, NOT because the cells are cancerous or you have cancer, but because the cells MAY (or MAY NOT) develop into cancer over a period of years. The exact relationship between VIN and vulval cancer remains unknown because so few studies have been carried out.

Generally VIN is divided into three stages — I, II or III — depending on how abnormal the cells are. VIN III is the commonest presentation among women and this means that the abnormal cells are present throughout the epithelium (remember it is only a millimetre thick!). In VIN I only a third of the cells in the epithelium are abnormal, whereas in VIN II, two thirds of the cells in the epithelium are abnormal.

What are the symptoms?

The symptoms do vary from woman to woman. Some have no symptoms and the area of VIN is noticed on a routine visit to the doctor. Other women complain of vulval pain or itching which can be quite severe. Others have irritation or painful sex. Some women even notice a lump or thickening of the vulval skin.

What do you find on examination?

Again, like the symptoms, this is variable among different women. Some women notice thickening or hardening of the skin and others have splitting or breakdown of the skin. Some women feel there is nothing wrong with the skin.

What investigations should be done?

VIN is diagnosed by a vulval biopsy where usually a small pea-sized amount of skin is removed from the affected area. Sometimes two or three biopsies are required. The procedure may be carried out under local anaesthetic in the clinic or your doctor may suggest that you come into hospital to have a biopsy removed under general anaesthetic.

A biopsy is essential so that the pathologists can see down the microscope to make sure the area is VIN (and not other skin conditions) and also to see exactly what degree of abnormal cells there are.

What causes it?

This remains unknown. There do appear to be two age groups who get VIN: women in their 60s to 70s and women in their 30s to 40s. In women in their 30s and 40s, VIN does appear to be associated with the family of 'wart' viruses (human papilloma viruses) which can cause change in the appearance of the cells down the microscope causing VIN to develop. VIN is noticed to be more common among women who smoke, but whether there is a direct relationship remains unknown.