Cancer occurs when the cells in a certain area of your body divide and multiply too rapidly. This produces a lump of tissue known as a tumour.

The exact reason why this happens in cases of vulval cancer is unknown, but certain things can increase your chances of developing the condition.

These include:

• increasing age
• vulval intraepithelial neoplasia (VIN)
• human papilloma virus (HPV) infection
• skin conditions that can affect the vulva, such as lichen sclerosus
• smoking

The risk of developing vulval cancer increases as you get older. Most cases develop in women aged 65 or over, although very occasionally women under 50 can be affected.

Vulval intraepithelial neoplasia (VIN) is a precancerous condition. This means there are changes to certain cells in the vulva that are not cancerous, but could potentially turn into cancer at a later date. This is a gradual process that usually takes well over 10 years.

In some cases, the abnormal cells may go away by themselves. However, because of the risk of cancer, treatment to remove the affected cells is often recommended.

Symptoms of VIN are similar to those of vulval cancer, and include persistent itchiness of the vulva and raised discoloured patches. See a GP if you have these symptoms.

There are 2 types of VIN:

• usual or undifferentiated VIN – this usually affects women under 50 and is thought to be caused by an HPV infection
• differentiated VIN (dVIN) – this is a rarer type, usually affecting women over 60, associated with skin conditions that affect the vulva

Human papilloma virus (HPV) is the name given to a group of viruses that affect the skin and the moist membranes that line the body, such as those in the cervix, anus, mouth and throat. It's spread during sex, including anal and oral sex.

There are many different types of HPV, and most people are infected with the virus at some time during their lives. In most cases, the virus goes away without causing any harm and does not lead to further problems.

However, HPV is present in at least 4 out of 10 women with vulval cancer, which suggests it may increase your risk of developing the condition. HPV is known to cause changes in the cells of the cervix, which can lead to cervical cancer. It's thought the virus could have a similar effect on the cells of the vulva, which is known as VIN.

Several skin conditions can affect the vulva. In a small number of cases these are associated with an increased risk of vulval cancer.

2 of the main conditions associated with vulval cancer are lichen sclerosus and lichen planus. Both of these conditions cause the vulva to become itchy, sore and discoloured.

It's estimated that less than 5% of women who develop one of these conditions will go on to develop vulval cancer. It's not clear whether treating these conditions reduces this risk.

Smoking increases your risk of developing VIN and vulval cancer. This may be because smoking makes the immune system less effective, and less able to clear the HPV virus from your body and more vulnerable to the effects of the virus.