The vulva is the outside part of the female reproductive system that opens into the vagina. There are two prominent skin folds, known as the labia majora, and two more barely visible, hairless skin folds called the labia minora.These inner and outer labia (Latin for lips) meet, protecting the vaginal opening and, just above it, the opening of the urethra (the short tube that carries urine from the bladder).

At the front of the vagina, the labia minora meet to form a fold or small hood of skin called the prepuce. Beneath it lies the clitoris, an approximately ¾-inch structure of highly sensitive tissue that becomes swollen with blood during sexual stimulation. At the lower end, just beneath the vaginal opening, is the fourchette, where the labia minora meet. Beyond the fourchette is the anus, the opening to the rectum. The space between the vagina and the anus is called the perineum.

Cancer of the vulva (also known as vulvar cancer) most often affects the inner edges of the labia majora or the labia minora. Less often, cancer occurs on the clitoris or in Bartholin glands (small mucus-producing glands on either side of the vaginal opening).

Over 90% of cancers of the vulva are squamous cell carcinomas, which means they begin in squamous cells, the main cell type of the skin. This type of cancer usually forms slowly over many years and is usually preceded by pre-cancerous changes that 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 pre-cancerous cells are confined to the epithelium (surface layer of the vulvar skin). VIN is often divided into three categories—VIN1, VIN2, and VIN3, with the last indicating furthest progression toward a true cancer.

Dysplasia is often used as another term for VIN. Using this terminology, there is also a range of increasing progress toward cancer – first, mild dysplasia; next, moderate dysplasia; then severe dysplasia; and, finally, carcinoma in situ. Most women with VIN or dysplasia will not develop vulvar cancer. However, we cannot predict which women will, so treatment of women with VIN is very important (see the section "Can Vulvar Cancer Be Prevented?"). In the past, cases of VIN were included under 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.

The second most common type of vulvar cancer (about 2% to 4%) is melanoma. Melanomas develop from the pigment-producing cells that determine the skin's color. This disease is discussed in greater detail in an American Cancer Society document "Melanoma Skin Cancer." About 5% to 8% of melanomas in women occur on the vulva, usually on the labia minora and clitoris.

A small percentage of vulvar cancers develop from glands and are called adenocarcinomas. Some develop from Bartholin glands, which are found at the opening of the vagina and produce a mucus-like lubricating fluid. Although most Bartholin gland cancers are adenocarcinomas, some (particularly those developing from the ducts of the gland) may be different types, either transitional cell carcinomas or squamous cell carcinomas. Adenocarcinomas can also form in the sweat glands of the vulvar skin, although this is quite rare.

Paget disease of the vulva is a condition in which adenocarcinoma cells are found in the vulvar skin. Between 20% and 25% of patients with vulvar Paget disease also have an invasive adenocarcinoma of a Bartholin gland or sweat gland. In the remaining 75% to 80%, the malignant cells are found only in the skin's top layer and do not involve the tissues under that layer. Since a tumor in the Bartholin gland is easily mistaken for a cyst (accumulation of fluid in the gland), delay in accurate diagnosis is common.

Less than 2% of vulvar cancers are sarcomas, tumors of the connective tissues under the skin that tend to grow rapidly. Unlike other cancers of the vulva, vulvar sarcomas can occur at any age, including in childhood.

Verrucous carcinoma resembles a large wart and requires a biopsy to distinguish it from a benign (non-cancerous) growth. This form of vulvar cancer is a slow-growing subtype of squamous cell carcinoma and tends to have a good prognosis (outlook for chances of survival).

Basal cell carcinoma, the most common cancer of sun-exposed areas of the skin, occurs very rarely on the vulva. It is discussed further in an American Cancer Society document "Nonmelanoma Skin Cancer."

Revised: 06/21/2006