Risk Factors for Vulvar Cancer

A risk factor is anything that changes a person's chance of getting a disease such as cancer. Different cancers have different risk factors. For example, exposing skin to strong sunlight is a risk factor for skin cancer. Smoking is a risk factor for many cancers.

There are different kinds of risk factors. Some, such as your age or race, can’t be changed. Others may be related to personal choices such as smoking, drinking, or diet. Some factors influence risk more than others. But risk factors don't tell us everything. Having a risk factor, or even several, does not mean that a person will get the disease. Also, not having any risk factors doesn't mean that you won't get it, either.

Although several risk factors increase the odds of developing vulvar cancer, most women with these risks do not develop it. And some women who don’t have any apparent risk factors develop vulvar cancer. When a woman develops vulvar cancer, it is usually not possible to say with certainty that a particular risk factor was the cause.

Age

The risk of vulvar cancer goes up as women age. Less than 20% of cases are in women younger than age 50, and more than half occur in women over age 70. The average age of women diagnosed with invasive vulvar cancer is 70, whereas women diagnosed with non-invasive vulvar cancer average about 20 years younger.

Human papillomavirus

HPV stands for human papillomavirus. HPVs are a large group of related viruses. They are called papillomaviruses because some of them cause a type of growth called a papilloma. Papillomas — more commonly known as warts — are not cancers. Different HPV types can cause different types of warts in different parts of the body. Some types cause common warts on the hands and feet. Other types tend to cause warts on the lips or tongue.

Certain HPV types can infect the outer female and male genital organs and the anal area, causing raised, bumpy warts. These warts may barely be visible or they may be several inches across. The medical term for genital warts is condyloma acuminatum. Two types of HPV (HPV 6 and HPV 11) cause most cases of genital warts, but are seldom linked to cancer and are known as low-risk HPV.

Other HPV types have been linked with cancers of the cervix, vagina, and vulva in women, cancer of the penis in men, and cancers of the anus and throat (in men and women). These are known as high-risk types of HPV and include HPV 16 and HPV 18 as well as others. Infection with a high-risk HPV may produce no visible signs until pre-cancerous changes or cancer develops.

HPV can pass from one person to another during skin-to-skin contact. One way HPV is spread is through sexual activity, including vaginal and anal intercourse and even oral sex.

Some doctors think there are 2 kinds of vulvar cancer. One kind is associated with HPV infection (more than half of all vulvar cancers are linked to infection with the high-risk HPV types) and tends to occur in younger women. The other is not associated with HPV infection, is more often found in older women, and may develop from a precursor lesion called differentiated vulvar intraepithelial neoplasia (discussed below).

Vaccines have been developed to help prevent infection with some types of HPV.

For more about HPV, see HPV (Human Papillomavirus).

Smoking

Smoking exposes people to many cancer-causing chemicals that affect more than their lungs. These harmful substances can be absorbed into the lining of the lungs and spread throughout the body. Smoking increases the risk of developing vulvar cancer. Among women who have a history of HPV infection, smoking further increases the risk of developing vulvar cancer. If women are infected with a high-risk HPV, they have a much higher risk of developing vulvar cancer if they smoke.

HIV infection

HIV (human immunodeficiency virus) causes AIDS (acquired immunodeficiency syndrome). Because this virus damages the immune system, it makes women more likely to get and to stay infected with HPV. This could increase the risk of vulvar pre-cancer and cancer. Scientists also believe that the immune system plays a role in destroying cancer cells and slowing their growth and spread.

Vulvar intraepithelial neoplasia (VIN)

Squamous cell carcinoma of the vulva usually forms slowly over many years. Pre-cancerous changes often occur first and can last for several years. The medical term most often used for this pre-cancerous condition is vulvar intraepithelial neoplasia(VIN). Intraepithelial means that the abnormal cells are only found in the surface layer of the vulvar skin (epithelium).

VIN is typed by how the lesions and cells look: usual-type VIN and differentiated-type VIN. It is sometimes graded VIN2 and VIN3, with the number 3 indicating furthest progression toward a true cancer. However, many doctors use only one grade of VIN.

• Usual-type VIN occurs in younger women and is caused by HPV infection. When usual-type VIN changes into invasive squamous cell cancer, it becomes the basaloid or warty subtypes.
• Differentiated-type VIN tends to occur in older women and is not linked to HPV infection. It can progress to the keratinizing subtype of invasive squamous cell cancer.

In the past, the termdysplasia was used instead of VIN, but this term is used much less often now. When talking about dysplasia, there is also a range of increasing progress toward cancer -- first, mild dysplasia; next, moderate dysplasia; then severe dysplasia; and, finally, carcinoma in situ.

Although women with VIN have an increased risk of developing invasive vulvar cancer, most cases of VIN never progress to cancer. Still, since it is not possible to tell which cases will become cancers, treatment or close medical follow-up is needed.

The risk of progression to cancer seems to be highest with VIN3 and lower with VIN2. This risk can be altered with treatment. In one study, 88% of untreated VIN3 progressed to cancer, but of the women who were treated, only 4% developed vulvar cancer.

In the past, cases of VIN were included in the broad category of disorders known as vulvar dystrophy. Since this category included a wide variety of other diseases, most of which are not pre-cancerous, most doctors no longer use this term.

Lichen sclerosus

This disorder, also called lichen sclerosus et atrophicus (LSA), causes the vulvar skin to become very thin and itchy. The risk of vulvar cancer appears to be slightly increased by LSA, with about 4% of women having LSA later developing vulvar cancer.

Other genital cancers

Women with cervical cancer also have a higher risk of vulvar cancer. This is probably because these cancers share certain risk factors. The same HPV types that are linked to cervical cancer are also linked to vulvar cancer. Smoking is also linked to a higher risk of both cervical and vulvar cancers.

Melanoma or atypical moles

Women who have had melanoma or dysplastic nevi (atypical moles) in other places have an increased risk of developing a melanoma on the vulva. A family history of melanoma also leads to an increased risk.