Looking closely at vulva cancer

In women, the external genitalia are collectively referred to as the vulva.  The vulva includes the labia majora (large lips), the labia minora (small lips), the clitoris, the mons pubis and the perineum.  The inner area between the labia minora is called the vulvar vestibule, which surrounds the openings of the vagina and urethra.  The vulva is covered by skin, which has an outer layer of squamous epithelium and some underlying glands.

The skin of the vulva and the lining of the vagina both have a relatively rich blood supply and lymphatic drainage.  The lymph channels from the vulva pass to the groin, while those from the vagina pass mainly to the lymph nodes in the pelvis.

Cancer of the vulva is uncommon, accounting for approximately 4% of gynae cancers.  Ninety percent of the cancers start from the skin surface (squamous cell carcinomas), but cancer can also start in glands under the skin (adenocarcinomas).  Melanomas occasionally occur on the vulva.  The average age at the time of diagnosis is 65 years.

Squamous Cell Carcinoma

There are two different types of vulvar cancer.  The most common form occurs in postmenopausal women and is usually associated with a long history of chronic vulvar itching.  The most likely cause of the itching will be a skin condition called lichen sclerosus, which affects around one in 80 women.  Lichen sclerosus can occur at any age, including children, but is most common in middle-aged and elderly women.  In most cases, it’s a lifelong condition.  It can be managed by using cortisone cream to reduce the itching, but it needs to be carefully monitored.  The chance of lichen sclerosus progressing to vulvar cancer is around 5%.

The less common type of vulvar cancer occurs in premenopausal women.  It’s likely to be linked with smoking and persistent sexually acquired infection with the human papilloma virus (HPV). Chronic HPV infection can cause a precancerous condition called vulvar intraepithelial neoplasia (VIN), which also causes itching or burning.  If VIN is not identified early and treated, the risk of progression to vulvar cancer may be around 30%.  This is similar to the way chronic HPV infection affects the cervix and vagina.  VIN can be treated by localised surgical excision or laser therapy, neither of which is likely to cause significant scarring.

Immunosuppression is another important factor.  This typically occurs after long-term cortisone or methotrexate treatment of a woman, who has a chronic autoimmune disorder or has had an organ transplant.  It’ll reduce the woman’s resistance to viral infection and cancer, making VIN and vulvar cancer more likely.

HPV vaccination, for teenage girls, was introduced in Australia in 2007, and a few years later extended to cover teenage boys.  This has already lowered rates of precancers of the cervix in younger women and will progressively decrease the rates of vulvar and vaginal cancer in the future.

Vulvar Melanoma

 Vulvar melanoma is the second most common vulvar cancer, typically affecting post-menopausal white women.  They’re classified as mucosal melanomas.  In Australia, approximately 10 women are diagnosed each year (one in a million), compared with over 4,700 women who are diagnosed with a typical skin melanoma (cutaneous melanoma).

Vulvar melanomas are typically diagnosed in their later stage, which increases the chances of them spreading to other areas.  The cause of vulvar melanoma is poorly understood.  They’re not related to sun exposure and gene mutations, which are important in cutaneous melanomas have not been found in vulvar melanomas, indicating these two melanomas are caused by different factors.

Paget’s Disease

Paget’s disease usually affects the nipple area of the breast but can occasionally affect the vulva.  When the disease affects the breast, there’s usually an underlying invasive cancer.

Vulvar Paget’s disease is commonly a glandular type of precancer (adenocarcinoma in situ) and only about 20% of cases have an associated underlying invasive cancer (adenocarcinoma).  The invasive cancer typically starts in the vulva, but may occasionally start in local organs, such as the bladder, urethra, or rectum.