What are the 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 without 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.
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 papilloma virus
Human papilloma virus (HPV) is a group of more than 100 types of viruses. They are called papilloma viruses 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. 2 types of HPV, HPV 6 and HPV 11, cause most cases of genital warts. These 2 types are seldom linked to cancer, and so are called low-risk types of HPV.
Other HPV types have been linked with cancers of the cervix 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, HPV 18, HPV 31, as well as others. Infection with a high-risk HPV may produce no visible signs until pre-cancerous changes or cancer develops.
HPV can be passed from one person to another during skin-to-skin contact. One way HPV is spread is through sex, including vaginal and anal intercourse and even oral sex.
About half of all vulvar cancers are linked to infection with the high-risk HPV types. HPV linked vulvar cancer is more common in younger women and is seen less often in older women. Some doctors think there are 2 kinds of vulvar cancer. One is associated with HPV infection and tends to occur in younger women. The other kind is not associated with HPV infection, and more often is found in older women.
Vaccines have been developed to help prevent infection with some types of HPV. Right now, 2 different HPV vaccines have been approved for use in the United States by the Food and Drug Administration (FDA): Gardasil® and Cervarix®. These are discussed in more detail later in this document.
Smoking exposes the body to many cancer-causing chemicals that affect more than the 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.
Human immunodeficiency virus
Human immunodeficiency virus (HIV) causes the acquired immunodeficiency syndrome (AIDS). Because this virus damages the body's immune system, it makes women more likely to get HPV and to stay infected with it. This may, in turn, 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
Squamous cell carcinoma of the vulva usually forms slowly over many years. Often, pre-cancerous changes occur first and may 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).
There are 2 types of VIN based on how the lesions and cells look: usual-type VIN and differentiated-type VIN. Usual-type VIN occurs in younger women and is caused by HPV infection. It is sometimes split into 2 grades, VIN2 and VIN3, with the number 3 indicating furthest progression toward a true cancer. However, many doctors use only one grade of VIN. 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 term dysplasia 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 VIN 3 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.
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) elsewhere on the body have an increased risk of developing a melanoma on the vulva. A family history of melanoma also leads to an increased risk.
Last Medical Review: 02/05/2013
Last Revised: 02/13/2014